If interested in the Stone Age origins of these passage burial mound tombs or Mesolithic hunter-gatherer menhirs, megalithic stone circles, dolmens, etc., John Waddell's The Prehistoric Archaeology of Ireland (1989) linked here is a good summary.

The Listoghil dolmen (passage grave) and tumulus (mound burial):  Evidence of a Mesolithic Hunter-Gatherer Solar Cult Continued and Adapted by the invading Celts

We can observe the continued archaeoastronomical alignments of the Celts' own megalithic mound passage tombs (tumulus/i and dolmens) of individuals which they continued to build long after the indigenous inhabitants of Ireland disappeared, aligned to Samhain (Oct. 31st) or Beltane/Beltain (May 1st) sunrises, or the An Grianstad (Dec. 21st) winter solstice.  In more places they appeared to modify the ancient mounds or continue their use, but in both respects the influence of the solar cult of the Mesolithic hunter gatherers is clear.

Celtic renovation of the ancient Meso-Neolithic burial mounds continued through the eighth century CE (700s).  Celts excavated the more ancient Stone Age burial mounds in order to construct new inner chambers or passages for new burials, initiation rites, and more.  Thus, the ancient burial mounds of the original inhabitants of the island seem to have been repurposed and continued by the invading Celts.  Archaeologists have uncovered deposits of excavation spoil (as new passages were dug into the ancient burial mounds erected by those displaced by the Celts) with scattered Neolithic human bones appearing in it, apparently separated from their original skeletal individuals (from mound burials being disturbed as new passages were dug and then buttressed) and (sacrificed) animal bones near Bronze and Iron Age Celtic constructions or modifications, construction that continued even through the late Medieval Period. 

In both regards, in solar or lunar alignments and later modification of burial mounds with new passages and artwork, we can see vestiges of the original solar cult now lost to the ages of the mysterious dark-skinned, blue eyed hunter gatherers who originally inhabited the island before being displaced by the Celts.  The Celts would continue the ancient passage mound burials by modification through annexing, appending, and connecting the hunter-gatherers' ancient mounds.  Their modifications of the ancient mounds continued into the Medieval Period (500s-1200s CE) well after the Roman (Irish Catholic) Christians earnestly attempted to eradicate pagan burial practices from the island. Incidentally, this indicates the overt and covert resistance and survival of Celtic beliefs and practices for centuries after the coming of Roman Catholic (Irish) Christendom.

The Tara Hill Tumulus:  Another Passage Tomb Tumulus of Mesolithic Hunter-Gatherer Origin with Samhain Archaeoastronomical Alignment 

The Killycluggin Stone Circle: Mesolithic Hunter-Gatherer Solar cult beginnings (~2500 BCE) with Celtic La Tène endings (~400 BCE-100 CE)

While the earliest associated Celtic Samhain archaeological evidence is associated with the Killycluggin Stone of its older Mesolithic Megalithic Stone Circle, so are the earliest and broadest allusions to Cromm in Christian annalistic evidence in the earliest sources, including: The Quarta Vita of Saint Patrick written c. 800 CE, The Vita tripartita Sancti Patricii written c. 1100 CE, The Metrical Dindsenchas (place lore poems) written c. 1160 CE, the 1290 CE The McGovern Duanaire, Book of Magauran, or Book of McGovern (book of Goidelic poems), and the 1636 CE Annals of the Four Masters.   Anglo-Irish historian, Classical Roman and Byzantine historian, and philologist (study of language in oral and written historical sources) J.B. Bury contended there is textual evidence that there may be a deletion of a passage about Cromm from St. Patrick's biographer Tírechán's Collectanea published between 688 and 693 CE.  Correlated from the cult icon's textual description in The Vita tripartita Sancti Patricii written c. 1100 CE with the topography on the Plains of Slaughter where the Killycluggin Cromm cult icon was erected, it'd appear that Cromm's face on the Killycluggin Stone faced towards the Tara Hill rath (circular earthwork fort) to the South.

These historical records corroborate or match the archaeological dating of Samhain traditions to the Killycluggin megalithic stone circle depicted in our logos, thus representing the truest Celtic birthplace for our traditions.  A more thorough discussion of Cromm's cult at the Killycluggin stone follows this section describing the early sites associated with Samhain. 

Tlachtga (Ward) Hill: The Place Samhain Survived and Spread

Unfortunately, his claim still circulates today, even among active academics and research archaeologists and probably has a lot more to do with tourism and securing funding for preservation and digs.

The earliest construction here dates to the Bronze Age (1200-800 BCE), much later than the aforementioned sites.  The latest building appears to have occurred between 400-520 CE in the early Medieval Period.  Tlachtga may have legitimately evolved by the arrival of the third century (200 CE) to become a central cultural hearth for the Druids for the celebration of Samhain in Ireland.  There appears to be a middle building phase between 800 BCE-400 CE, currently the least understood by archaeologists.  It was certainly the place Samhain traditions survived and continued into the Medieval Period after Christians stamped it out near the Killycluggin Megaliths in the early centuries.  

According to early histories the Tlachtga Celts (and their Samhain Great Fire Festival) began with the Luigni, an Erainn Celtic tribe to fertility goddess Tlachtga, daughter of the deified Druid sun god Mug Ruith (analagous to the pan-Celtic Lugh), thereby as his heiress, a sun goddess.  So, it appears that Cromm's cult had a rival thirty miles away by 200 CE in the Ward Hill (Tlachtga) ring hill fort.  Yet, the County Cavan Killycluggin Megalithic stone circle (associated with the cult of underworld, fertility, and harvest god Crom Cruach) site appears centuries older (from its La Tène curvilinear designs), dating 400 BCE-100 CE compared to Tlachtga's (400-520 CE) Celtic constructions, so better represents more original Celtic Samhain belief and traditions.  Ironically, Tlachtga's cult at Ward Hill, actually can be construed as parallel evidence for the evolution of Lugh's solar festivals (to give Lugh power to escape darkness and winter) into more solemn rites placating Cromm's tributes to ensure Lugh's return.  Her identification with her father as a deified Druid solar deity Mug Ruith in Irish mythology seems to provide clear textual evidence that Samhain traditions likely originated in solar worship.

The Tlachtga hill ring fort mound passage burial was likely influenced by Cromm's older cult in just being thirty miles from the Killycluggin stone circle with Tlachtga replacing sun god Lugh as a stand-in for her father, and her association with fertility and the harvest.  Or it could be just as likely that the Celts around Tlachtga evolved their own solar cult and mythology independently. But Tlachtga's Samhain cult appears to have transferred to Tara Hill after it was invaded and colonized by a rival tribe, the Lagin, who moved the seat of royal Celtic power to Tara.  13 miles from Tlachtga (Ward) hill was the Hill of Tara, long the seat of the High Kings of Ireland.  

Consequently, we can only suggest that the evidence points to Halloween starting at the Killycluggin stone circle with Cromm's cult despite Keating's now debunked 17th Century competing claim about Tlachtga (by the discovery of Cromm's circle in 1921 and 1954) despite what the tourism bureau and guides tell us because Killycluggin's stone circle is actually centuries older.   

The Hellcave Sidhes to the Otherworld

These "hell caves" were supposed to connect to the Keshcorran Caves in County Sligo by a tale of a maiden dragged by a cow's tail from the Cave of the Cats to them, and of course the Tír na nÓg (Teer-na-nohg) subterranean Otherworld of immortals, monsters, demons, creatures, fairies and elves.

In the Irish myths, there were two remaining other ancient "Great Burial Mounds" associated with sidhe portals to the underworld from which the departed and supernatural creatures could enter our world at liminal Samhain and Beltaine in addition to the burial mound atop Oweynagat Cave of the Cats:  

1. Tlachgta Hill (already aforementioned) & 

2. Teltown's Burial Mounds.  

Of course Donn's Island sea mouth represents a fourth, with Donn possibly replacing Cromm as Irish mythology marched through the ages (mentioned and pictured in the upcoming section on Celtic Cosmology and the Celtic Otherworld).  

It can't be doubted that these portals were places where annual ritual deposits have been found to supplicate Cromm, Morrigan, Medb, or any of the supernatural beings that lived in the Otherworld in solar rites dedicated to ensuring the sun's triumph over winter.  

But the archaeological dates at Oweynagat just don't support it as the birthplace of Halloween.  It was a major cultural hearth of Samhain like Tlachgta served through the late Medieval Period.  But the oldest parts of the complex's construction dates from the Neolithic to Bronze Age (4000 BCE-400 CE), associated with and constructed by our dark-skinned hunter-gatherers.  But the more significant Celtic features of the chambers inside the burial mound in its souterrain passage and tunnel construction (associated with Samhain rites and myths there) date to the Early Medieval Period (400 CE-1100s CE), again bested by the central Killycluggin Stone's curvilinear La Tène designs by centuries.  

Most of the passages in the burial mounds here in the Boyne Valley and at nearby Knowth (near Newgrange) all date from the Early Medieval Period, and many of them were dug to connect to each other indicating they had more spiritual than storage significance.  The current souterrain passage into the cave's Ogham inscriptions suggest it can't be earlier than the 4th-6th (300s-500s) Century CE (which didn't exist before then) and the souterrain construction methods are definitely dated to the middle half of the 8th Century CE (~750s CE) to the first half of the 13th Century CE (~1250s CE), dating relatively from other souterrain Celtic construction in Ireland.  We know Celtic constructions here began centuries after those at Killycluggin. While no doubt Samhain festivals happened annually at Rathcroghan's royal complex of Connacht for centuries, and it is one cultural hearth, it's not likely the birthplace claimed dubiously by Curley.  

The function of these myths could have been initiation rites in warrior culture or perhaps instructed that natural nature of the social stratification and hierarchy of warrior and Druid elites as bringing order the chaos of the Underworld, to effectively scare commoners into submission to their will much like cthonic myths worldwide do.  And of course they all provided explanations for misfortune—from drought to crop failures to disease and stillborn livestock or children or miscarriages.    —

But to the Irish Celts, the Otherworld was called Oisin in Tír na nÓg (🔊 also known as Mag Mell and Emain Ablach), or the Land of Youth and was often associated with water (under or around sacred wells, across a sea, in a lake, etc.).  To the Welsh Celts, there was Annwn, Annwfn, or Annwfyn.  It was called Avalon in the Arthurian Brittonic Celtic folklore.  

The first century Roman poet Lucan reported that the Irish Celts believed departed human souls went to the Orbis alius (Latin), or Otherworld, who gather before the former mortal "lord of the dead" Donn in Tech Duinn or the "House of Donn" on his stormy island associated with Bull Island off the Beare Peninsula before departing to the Otherworld for a time before eventually being reincarnated (or deified [turned into a god]).  Celtic belief in reincarnation can explain the deification of former Druids and Druidesses into gods and goddesses imbued with immortal power. 

But elsewhere some accounts have Donn, despite his misleading moniker as lord of the dead, serving as Greece's Charon did to ferry the dead across the River Styx into Hades, for Charon didn't rule Hades.  Hades did, just as Cromm ruled the Celtic underworld.  So either Donn is derivative of Cromm, or is his minion whose function is to gather then ferry souls to the Otherworld like the later personification of Death in Christendom. 

In Celtic mythology, there are many chthonic (underworld) deities associated with death, dying, and the Otherworld to wit (including, but not limited to): 

Arwan (ruler of Annwn, Welsh ruler of the Otherworld);  Gwynn ap Nudd (another Welsh underworld god), Manannan mac Lir (Welsh ruler of the liminal spaces between the spirit world and ours);  The Cailleach (the Welsh lord of the dark half of the year, storms, and the dying of crops); Aed (the prince of the Daoine Sidhe and god of the underworld); Cerridwen (a goddess of the underworld, also the goddess of rebirth and transformation); Manannan (The God of the Otherworld and Sea); Donn ("the Dark One," associated with shipwrecks and sea storms, he gathers the dead on his stormy island before they depart for the Otherworld); the Goddess Morrhigan (who decided if you died in battle); Cernunnos (protector of the souls of the ancestors in the Underworld, guided their rebirths in the mortal realms); and Bilé (The Irish god of death, Gaelic/Goidelic iteration of older Bryonthic [Welsh] god Bel or Belinos for which Beltane/Beltain was named [19th Century Celticists John Rhy̌s and M. H. d'Arbois de Jubainville insisted Bilé/Bel/Belinos was god of darkness and death in the underworld, an opinion no longer shared by serious Celticists and the result of sloppy linguistic scholarship]; according to mythology, Bilé/Bel/Belinos was a sacred oak nurtured by the mother of the good gods Danu, the mother of all the Tuatha (the good Irish Celtic deities), and giving birth to the "all good" overgod  of the Tuatha, Dagda).  

It turns out that separated in small villages and migrating by fits and starts over many centuries, especially in contact with other Indo-European people (through, for example, the Greek colonies in Marseilles [France]) produces a dazzling and dizzying array of creatures, gods, and cosmologies (conceptions of the universe, this world, and afterlife) and as many chthonic gods. 

And, no, Samhain is NOT the name of the Celtic lord of darkness or death, contrary to the bad scholarship of British Colonel Charles Vallancey writing in the 1770s (exposed by folklorist W.J. Bethancourt III, in his 1994 essay Halloween: Myths, Monsters and Devils) that ended up appearing in the campy 1980s Christian Jack Chick Tracts (Christian evangelical religious pamphlets).  Nor is Cromm Baal.  Both of these links will help you understand those long-standing misunderstandings. 

Cromm: THE Goidelic Fertility & Underworld God

But according to the Annals of the Four Masters, a compilation of the earliest Irish histories compiled in the 1630s, Cromm Cruach is perhaps the first and oldest iteration of the Irish Celts' chthonic lords of death and the Otherworld or Underworld.  Cromm, quite clearly, is among the oldest of the old Celtic gods. 

Vallancey's fancies (about a god he made up called Samhain based upon a minor human character in a myth given the name of the fall solar cult rite by the same name) are like the equally wrong insistence of Rhy̌s and Jubainville about Bilé/Bel/Belinos being a dark god of the underworld versus the truth of Bilé in an Irish mythological sacred oak.  Their error in the 1800s led Victorian scholars to wrongly conflate the Goidelic Celtic Bilé/Bel/Belinos through false linguistic associations with the Sumerian Baal through false etymology, and thereby also the child-eating Greek Cronos, the biblical Sumerian derived Canaanite fertility and underworld child-eating deity Moloch, and the Sumerian god Baal, and subsequently, the devil. 

Some scholars suggest Cromm was the Greek Cronos (father of the Olympians who ate his children and lead Titan), or influenced by ideas of him as an underworld child-eater equated with the Greek understandings of the biblical Canaanite (Sumerian derivative) underworld fertility god of Moloch.  They do so on the basis of  the Medieval Irish tale of “The Siege of Druim Damhgaire," with Lugh's (the light bringer's) triumph over Fomarian Baylor (darkness) tracking Zeus' victory over Cronos.  The implication from this medieval tale is that Baylor is Cronos and Cromm and Lugh is Zeus or the biblical Yahweh, or Cromm with St. Patrick.  The 12th-century (1100s CE/AD) Dinsenchas poem records a fabled confrontation between Crom Cruach and Saint Patrick, but thus described Cromm: 

“At Magh Slecht used to stand a lofty idol,

whose name was the Crom Cruach;

it caused every tribe to live without peace.

The valiant Gael used to worship it:

with tribute they asked of it their share in hard times.

He was their god, the wizened Crom, hidden by many mists:

those that paid him tribute shall ne’er see heaven.

For him ingloriously they slew their firstborn,

to pour the blood round Crom Cruach.

Milk and corn they asked of him.

From his worship came many crimes to Magh Slecht.

Thither came Tigernmas, prince of distant Tara, one Samhain eve,

with all his host, to meet their sorrow.

They stirred his evil eye, they beat their fists,

they bruised their bodies, wailing to the demon who held them in thralls,

they wept storms of tears, weeping prostrate.

Dead the men, void of strength. Hard their fate.

One man in four there made his escape with death on his lips.

Round Crom Cruach there the hosts did obeisance:

though it brought them under mortal shame,

the name cleaves to the mighty plain.”   

The 12th Century Dinsenchas is suspect in being anti-Celtic Irish Catholic Medieval propaganda against the old Celtic cults in recording how King Tigernmas, who introduced Cromm's worship according to the Dinsenchas, had a three-fourths of his host smited by Cromm.  It also triumphantly records Cromm's cult icon's destruction by Saint Patrick who would stamp out Druidism, just as Lugh had overcome the Fomarians, and Dadga/Lugh overcomes Cromm.  

Cromm means bent or broken in Celtic Gaelic, and Cruach means pile or stack and refers to hills or mountains that look like stacks or piles of corn or grain.  Thus the Celtic underworld boss Cromm's name appears to be eponymous and toponymous in that the deity's name describes the actual physical appearance of Cromm's central stone icon and twelve surrounding stones upon the Plains of Slaughter (a three mile square tract of land in central north Ireland situated in the south-eastern part of the Parish of Templeport, Barony of Tullyhaw, in the west of County Cavan).  Cromm is known colloquially as The Crouching Darkness, or The Bent One of the Hill, and is depicted as a wizened old man shrouded in mist. His holiday heralded the end of summer and beginning of winter.  

Cromm may also be derived from cenn meaning head or chief as well or cruim meaning thunder.  However, these proposed origins may represent false etymological associations (word origins) in a likely erroneous attempt to equate Cromm with Zeus, Ukko, and Oden/Thor, as both Indo-European and Finno-Ugric pantheons of gods tend to be ruled by lightning, weather, or sky over gods.  Also, Tiranus, not Cromm, was the Celtic god of thunder.  Nor was lightning or electricity associated as a power of either Dagda or Cromm, although Dagda could control weather by playing a harp, so there is a chance thunder could be linguistic residue from Dagda.  Also, derivation from cenn's head or chief could serve as linguistic evidence of Cromm's derivation from Dagda, who was the original chief of the Celtic gods. 

However, the modern English moniker of The Bent One of the Hill by which he's known colloquially known today seems to indicate the more accurate understanding of his name described the physical appearance of his cult icons situated on the plains where they were erected, just as the silhouetted appearance of the Celtic Britonic Stonehenge's appearance on Salisbury Plain near Wiltshire, England has become similarly iconic and the stone circle's English name describes the icon itself.  

More description and explanation is required to understand Cromm's actual megalithic icons of the Killycluggin Stone and its twelve surrounding stones depicted in our logos, but first the solar cults that explain them require elucidation, pun intended (to elucidate means to enlighten).  For example, some Celticists insist Cromm's central Killycluggin Stone and its twelve surrounding megaliths are evidence of a solar cult on the basis that the twelve surrounding stones represented the twelve ecliptic constellations of the Zodiac in addition to the folklore chronicled in The Annals or earlier sources.  

May Day's (May 1st) Beltane was definitely devoted to Lugh by any other name throughout Gaul, the Roman name for their then-unconquered frontier peopled by uncivilized barbarian semi-nomadic pastorilists who herded sheep and cattle and practiced horticulture in limited farming, and those remaining foraging bands who still hunted and gathered.  

In other words, Gaul (Gallia in Latin) was the land of the Celtic peoples of the British Isles and Western Europe although it's most often used to refer to continental mainland Gaul.  In Central Europe, tradition holds Belenus or Beil, the Goidelic and Gaelic Lugh's Gaulic counterpart—all of them being solar deities like Greece's Apollo—is the namesake of Beltane (and thus the name of the holiday isn't a reference to the Sumerian Baal as commonly misunderstood owing to pseudoetymological error, but rather the same god as the Goidelic, Gaelic, and Brythonic Lugh).

Lugh's May Day Beltane festival marked the start of the light half of the year and the bright return of Lugh from his epic yearly struggle with darkness.  Beltane in Gaelic means bright fires if not derived from Bilé/Bel/Belinos the sacred oak (personified in later mythology as god of healing and fire) from whence Dagda sprang, here too tying Lugh and Dagda to Beltane.  

The May Day festival was the second of two liminal (threshold between the dark and light halves of the year) holidays of the Celtic year following the first of two in October's Samhain in which the dead and otherworldly spirits and supernatural creatures and beings found it easier to manifest themselves in our living world. 

The fire jumping traditions of Beltane when youth leaped over bonfires three times marked when to turn the cattle out to pasture after winter and prepare to plant crops for tending in the fields.  As the Celtic day began and ended with each sunset, so too did the Celtic year begin with "solar night" or the start of the dark half of the year (Oct. 31st to May 1st, preceding the light half between May 1st and Oct. 31st).  So the two liminal festivals marked the turning of the year from light to dark (first) and then dark to light (second). 

Otherwise, if not originally devoted to Lugh, the Celtic sun god, it is thought to have been devoted to the chief Celtic "good god" of life and death Dagda.  Dagda's Samhain would have involved supplication appealing to him to intervene to ensure the safe return of Lugh in the spring, and lend his great grandson an assist.  His powers and domain in Irish mythology are limitless as chief of the gods with power to compel the other gods.  Lugh's daily appearance in the sky in the fall after Mabon (September 24th) shrank with each passing day.  His increasing daily absence accelerated in ever shortening hours of daylight after Samhain (October 31st) until the Winter Solstice of Dec. 21st.  The arrival of the shortening of days foretold and marked the annual march of the seasons and the annual death of crops and livestock that winter brought.

Lugh (like the Roman god Vertumnus) was believed to cause the ripening of the fruits of the field in mid- to late- summer.  So the August 1st Lughnasadh or Lammas, one of the four cross quarter holidays of the Celts, is named after him.  It was named after him because it marked a change of the seasons in being halfway between the start of summer (Beltane, May Day, May 1st) and the Mabon autumnal equinox when harvesting began (Sept. 24th).  These festivals helped ancient celtic pastoralist ranchers and horticulturalist farmers keep track of time as Lughnasadh reminded them as much time had passed since planting as laid ahead before the harvest must begin.  Druids were keepers of these calendars and stone circles and tunnel burials with archaeoastronomical alignments with certain constellations or stars at certain points of the year to direct the annual tasks of the agrarian people, the keepers of the fire so to speak in a calendar of the Celtic year round.

Lughnasadh then signaled the approaching harvest season starting with the Celtic Mabon on September 24th (the autumnal/fall equinox) which ended on Samhain (October 31st, ushering in the dark half of the year).  Harvest started with Mabon and ended with Samhain.  Thus Samhain marked the last hours of twilight before annual sunset in the metaphorical solar cycle round of the year—Goidellic twilight.  The arrival of winter was actually the start of the next year, like slumber before one's day begins.  And although it may seem foreign to us today, it was actually more in tune with nature's cycles with autumn mating seasons meaning winter incubation of spring offspring and many varieties of early seeds planted in the fall lain dormant to awaken and germinate effortlessly in the spring.

Precise understanding of the original deity to whom Samhain was at first devoted seems to have been lost to the ages as the Celts had no written language and early Roman sources and later medieval sources are dubious, confusing, and contradict each other—and could represent misunderstandings of their authors to whom the Celts were foreign and largely hostile.  The earliest written sources are Roman sources (Catholic) from the 7th-9th Centuries (600s-800s), and digests of them from the 17th Century (1600s). In all cases, these accounts were written by Roman Catholic Christians hostile to Celtic paganism and intent on wiping out their cults and strongholds, an effort being undertaken in the first century CE by the Romans in Britain. 

It was Cromm who definitely subdued the sun each winter, and ruled the domain where departed human spirits dwelt, so he was definitely vilified at least by the 17th Century Christian compendiums. Thus, Cromm appears to be a derivative deity from Dagda who used to be the god of life AND death but by the time the Romans arrived had evolved to be the "all good god" of only light and life with Cromm now serving as the god of darkness and death which is how Christians equate him with the devil, but to do so shows profound willful ignorance of Celtic or even Jewish or Christian folklore, mythology, theology and cosmology.     

However, oral tradition (stories passed down by word of mouth by ancestral Celts) and the later historical accounts (Roman and Irish Medieval, and 17th Century sources) trace Samhain definitively to the cult of Cromm Cruach (known to commoners as Cromm Dubh), the Celtic God of the Underworld—not to be confused with the Canaanite/Sumerian God of Baal mentioned in the Holy Bible who Judeo-Christians by then had conflated with the devil, the lord of hell.  

Because anyone can stumble upon sources insisting Samhain supplicated Dagda, Lugh, or Cromm, it was important to explain the nuance, diversity, and evolution of Celtic belief as well as the permanent limitations of our source material in being scant, contradictory, and written by hostile cultural outsiders millennia and centuries later in deciphering either their authenticity and validity.  While this proposed evolution of Samhain cosmology (its possible earliest devotion to Dagda which evolved over time into devotion to Lugh or Cromm) is speculative based upon contradicting sources, it's reasonable just as the trimurti (Brahma, Vishnu, & Shiva becoming integrated with Indra) evolved in Hinduism as Dravidian animism was influenced by the beliefs of Aryan invaders that Dagda gave way to Lugh and Cromm and devotions on Samhain probably evolved to supplicate those deities over time in that order. 

So, it appears in ancient times from contradicting sources, Samhain rituals may be interpreted alternately to: 

(I) supplicate the "good god" Dagda to use his omnipotent power to ensure Lugh's freedom from the grips of the underworld spirits or beings subduing him, who would eventually be personified and deified as Cromm, or 

(II) to give Lugh the direct power (by enhancing his heat and power through burnt offerings) to escape Cromm through burnt offerings to Lugh on Samhain by immolation (fires being local manifestations of the sun), or, 

(III) to gravely and solemnly give due tribute to Cromm, in paying the annual tribute, tax, or ransom to guarantee Lugh's liberation in the spring, just as the Tuatha gods of light once were forced to pay a third tribute to the Fomarian gods of darkness 

Perhaps by the time the Romans left the British Isles, Celtic Samhain sacrifices continued in secret were made by invocation to potentially their over god Dagda, their sun god Lugh, and/or their death god Cromm alternately depending upon the individual, family, or village, or all at once.  Maybe it varied from family to family and household by household. Perhaps over the ages, as each succeeding generation of people had more time to contemplate death, they seem to have developed more involved and complex supernatural explanations for death or aspects of death became deified, and regional differences developed.

But by the time of Roman contact, all early sources agree, Samhain became more strictly the domain of the god of death and the underworld Cromm, the wizened bent one shrouded in mist, indifferent to the affairs of humans and demanding tribute for release of his hostage sun god Lugh.  It certainly was one way to answer a child's question about why there are seasons and why winter exists.  The lord of the Otherworld or darkness simply captured and subdued the sun once a year who demanded ransom to release his hostage.  It fits the mood of a dreary, cold, and rainy winter, and reinforced the truth of eventual triumph of the light Tuatha led by the ascendant son Lugh over the dark Fomarians who once exacted a third tribute, just as Cromm is alleged to have demanded in scions or firstborn livestock.   

But it appears that the Celtic over god Dagda and his cult, over time, was replaced by the cult of the sun god Lugh who would replace him as king of the Tuatha de Dannon gods of light after he led their forces in the second battle that banished evil Fomorian sea demons of darkness back to the sea in a metaphorical victory of light over darkness.  Later, Lugh's negative aspects in his duality of both lightness and darkness (likely inherited from the older cult of Dagda as the good god of light and darkness, life and death), codified in both his mixed good (Tuatha) and evil (Fomarian) parentage, led to the eventual deification of Cromm as a separate deity and god of the underworld or death, and his Samhain rituals from which our modern ones evolved.

How Christians Confused the Celtic Underworld Boss Cromm Cruach with the Sumerian Baal and Biblical Devil

Baal's Story & The Neolithic Agrarian Revolution

Astronomically, first day of summer rites in many cultures have often been associated with cattle with the sun in the constellation Taurus, the bull.  In ancient societies from the first cattle pictographs (picture writing that precedes syllabary and a phonetic alphabet in the evolution of writing) at Çatalhöyük that would eventually lead to the first Sumerian cuneiform writing system, to the Sumerian overgod El and his son Baal and their eventual cthonic underworld biblical Moloch, to the Greek Cretan Minoan Minotaur of King Minos on Crete, to the ritual sacrificial rites of Celtic Samhain, cattle have ancient associations with the first days of summer when they would be turned out to graze.  It's no accident because cattle domestication, the Neolithic Agrarian Revolution, drastically changed how humans on earth lived in exploding their population, enabling cities, civilizations, and empires.   

El, chief god to the Sumerians (like Zeus was to the Greeks) was the literal father of all of their gods.  El means the god or creator and his symbol was the bull which is son Baal would later inherit.  Agriculture developed during the Natufian Neolithic Agrarian Revolution (11 KBP-9 KBP [~9,000-7,000 BCE]) in the Fertile Crescent of the Middle East of Mesopotamia between the Tigris and Euphrates Rivers in modern day Iraq.  It wasn't until roughly 3500 BCE that the first true civilizations, or empires, in Sumer and Egypt had emerged, taking roughly some five millennia to develop after the domestication of the first plants (~11 KBP, ~9,000 BCE) and then animals (~9 KBP, ~7,000 BCE).  

Before, people lived in small bands of 20-50 people governed by chieftanships, women possessed more power because they produced a majority of our food through foraging than men did by hunting, and people were more equal and had more leisure time, but their total population numbers were limited by natural carrying capacity of their habitats like all animals.   People migrated following animal herds or seasonally migrated to take advantage of certain plants flowering or ripening or the arrival of insect swarms.   After farming and ranching, populations grew, technological advancement increased, annhilative warfare appeared, inequality between people and genders grew, and people lived in cities. 

The first civilization that produced the first complete writing system in the world, cuneiform (predating Egyptian hieroglyphs by ~300 years, Sumerian cuneiform developed around ~3500 BCE compared to 3200 BCE for Egyptian hieroglyphs by comparison): the Sumerians.  Sumer was the first civilization that developed in the Fertile Crescent of Mesopotamia of Iraq on the crops and animals the Natufians domesticated developed the first cities in barley and wheat and sheep, pigs, goats, and cattle.   Cities like Jericho and Ur and Uruk and their empire laid the foundation for the derivative Babylonian, Akkadian, Assyrian, and Persian empires who grew from the foundations Sumer laid, overpopulated themselves, and then laid waste to neighbors and assimilated them over the same region which lent itself geographically to the development of conquest and empires at the commercial crossroads of Asia, Africa, and Europe who would in Classical Antiquity subsequently face Classical Greek (in the Persian Wars), Hellenistic Greek (in Alexander the Great's conquest of the ancient world which laid the foundation for the Romans), and then Greco-Roman Civilization (in their domination of the Mediterranean world and the continent of Europe).   

Historical archaeologists and anthropologists suggest that the Genesis story of the murder of Adam and Eve's son Abel by Cain in the Garden of Eden in the first fratricide in Cain's murder of his brother Abel told in Chapter 4 actually captures the transition from nomadic foraging (hunter-gathering) to settled pastoralism (ranching) and farming (to agriculture and civilization).  It turned out that domestication of animals was more important than domestication of food crops because hooking a plow to a cow drastically increased food production and suprluses and dramatically increased human populations and freeing them from the search for food.  The preference of the biblical God of Abel's sacrifice of the fat of the firstborn of his flock (Hebrew: צֹאנֹ֖ו (tzo·nov); tson: small cattle, sheep and goats, Strong's Concordance 6629; NASB translation: lambs or sheep), causing Cain's jealousy and fratricide of his brother captured this transition and supernatural endorsement of the domestication of animals and served as a nod to the Hebrews to continue it.  

God, being more pleased by a blood sacrifice of an animal over Cain's sacrifice of the fruit of the soil in plant sacrifice captures the radical transformation of human life brought by the Agricultural Revolution that spurred civilizations across the planet after the last Ice Age.  It represented probably the most radical revolution in the entirety of human history or prehistory, so it can't be understated.  It simultaneously explains why some nation-states are rich and powerful today and others are not, and why some individuals and families are and others not.  It explains human inequality as well as enhanced tribalism and warfare.    

Farming and ranching meant that the human population would rapidly increase, leading to civilizations or empires across the world to arise and interact and attempt to conquer and dominate other empires—or those aboriginal, indigenous nomadic foragers and pastoralists without the advantages farming and ranching brought.  The Roman Empire likewise subjugated the pastoralist Celtic Britons' due to those advances.

When the Natufians first hooked cattle to a plow, they transformed the productivity of the land which enabled much larger settled populations of humans and an explosion in technological innovation.  More people meant as more connections between individuals and different communities grew, the greater the diversity in information and cultures that would develop.  More people also meant more potential innovators, leading to the relatively rapid technological advancement of humans ever since, explaining the acceleration in the pace of technological advancement.  People could now accumulate and improve knowledge enabled by writing and the collective learning that resulted from freeing people from the never ending quest for food—enabling job specialization and social stratification/hierarchy and ultimately technological advancement through irrigation, textiles, plumbing, religion, advanced technology, etc.   

El's Cult Challenged by Baal's Cult:  Attempted Religious Patricide Results in Moses' Filicide

Thus, it's no wonder that the Canaanite god of El is symbolized by the bull as cattle, more than any other domestic crop or animal, led to a revolution in the way humans lived on earth. In the same way the biblical God (Abraham's God, El) approved more of blood or animal sacrifice than plant or crop sacrifice, the domestication of animals more explained our development than farming ever could.  Oddly enough, initially and over time, El's son Baal became associated with the harvest of the field while El himself remained more associated with livestock, just as Cain was associated with the field and AbEL with livestock.  It's no wonder the biblical Yahweh more approved of Abel's sacrifice than Cain's because livestock had real consequence to human lifeways.  The Genesis story seemed to be God's approval of the domestication of animals and admonishing his creation to do more of it.  However, contrary to its biblical endorsement, for unknown reasons, over time, Baal's cult increased in popularity, meaning that El's cult shrank as Baal's increased.

This seems corroborated by recent discoveries in the early 21st Century at Göbekli Tepe in Turkey seem to indicate an animal worshiping religion predated and preceded the appearance of ivilization or empire itself (until recently, associated archaeology suggested religion comes from civilization, not the other way around).  El's older cult, whose symbol is the bull, can thus be equated with the cattle domestication cult.  Therefore, it tracks these recent discoveries about an older animal worshiping cult suggesting animal domestication was key in the development of religion.  But as the crop domestication cult in El's son Baal's cult rose, most associated with the harvest and fertility, El's cult began to decline, and El's symbol in the bull transferred to Baal in cattle, and along with it El's associations with cattle domestication.  

It could track the strange burial of the old icons at Göbekli Tepe, just like the older Egyptian polytheistic pantheon's devotees tried to wipe Pharaoh Nefertiti's sun-god Aten monotheism from history and memory.   Newer cults threaten older cults, and the older cults often respond violently and afterwards justify the same religiously. Perhaps Baal's cult endeavored to stamp out the older animal domestication cult, and it backfired to boomerang in its own destruction.

Thus, in this manner, El's son Baal became associated with fall harvest and fertility festivals—that is, farming and ranching.  The cultural and religious ideas of the Indo-Europeans from Central Asia who migrated into Europe deep in prehistory, the ancestors of the ancient Celts, traveled with them.  And that's exactly the source of the error that still circulates, wrongly connecting Cromm with Baal on the basis of them being both fertility and harvest gods.  Thus early linguists and scholars of comparative religion and mythology falsely made Cromm the analogue of the Sumerian Baal as harvest and fertility gods but ignored that Cromm's actual function to the Celts was more analogous to Sumer's Nergal as underworld boss of the dead.  And thus they wrongly associated Celtic Samhain with Satanism. Baal (the Sumerian god of fertility [like the Roman Bacchus or Greek Dionysus]), was being worshipped alongside his father El in the land of Canaan.  Baal would eventually supplant El, becoming the king of the gods in the Sumerian pantheon and replacing his father El.  Baal's popularity overrode his father's cult.  Both were being worshipped as the one true God simultaneously by the Sumerian Canaanites, and both had vigorous cults.  

The father of Judaism (via Isaac), Christianity (via Isaac's descendant Jesus Christ), and Islam (via Ishmael) was Abraham (alternately, Abram).  Abraham's cult to El (ELShaddai, ELohim, IsraEL) succeeded in stamping out the then ascendant but competing god Baal's worship when the Levites killed 3,000 golden calf worshipers of Baal (his father's iconography and domains eventually were transferred to Baal).  The son's cult was wiped out by the father's cult in filicide, and the rest is recorded in the Holy Bible.  The destruction of Baal's cult is recorded in Exodus 32 by Moses' commandment with the rest of Baal's worshipers finished off by plague.  So, eventually, El's cult destroyed Baal's cult, became Judaism, and the rest is the history of Judeo Christianity and Islam, the Abrahic faiths of the Bible.  Thus Baal's cult was demonized ever after by the Jews and Christians and Muslims consequently.  And the parental abuse of Baal's cult that initially threatened El's ultimately led the father's cult of El to triumph, and ever after its devotees demonized remnant Baal cultists to ensure that Baal would eventually become synonymous with evil and the devil/Satan—just as El's cultists had demonized Baal's devotees in a similar manner.   

It's through that convoluted process that the Celtic Cromm is often confused with the Sumerian Baal because both were fertility and harvest gods with festivals in the fall.  As Indo-Europeans brought their religious cults with them as they settled Europe and migrated into Europe from Central Asia and the Middle East (from Mesopotamia) over the centuries.  As a result,  there are both accurate or valid and false linguistic cognates (when those who study mother and daughter languages over time can make errors because of mistaken similarities in word roots).   

In the same way Cromm evolved from joyful and festive Dagda or Lugh fall solar fertility traditions of thanksgiving into far more somber remembrance and contemplation of the certainty of death, those original Indo-European religious beliefs hailing from the Sumerian, Egyptian, and Babylonian origins likewise continued to evolve and change.  As a result of attempts to find common language roots and origins, Judeo-Christians had a tendency to lose nuance and generalize, lumping all pagan festivals to nature fertility gods of the harvest together, they did the same with those that more solemnly or frightfully contemplated death, life after death, the underworld, and the annual death of winter, and, in turn, to equate them with devil worship.  Thus, in this way, attempts to understand "other" were perverted in vilifying or demonizing "other" in equating Baal with Beelzebub and the god of healing Biel for whom Beltane was likely named, and eventually Celtic Cromm as analogous because he was the god of the Celtic underworld like Beezlebub and Satan became synonymous as other names for Satan the great deceiver.   

As Christian monks and missionaries undertook the study of others as scholars to report back to Crown and Pope, and undertook the study of the cultures of people different from themselves and record their histories, they made sense of their beliefs and practices by relating them to analogues more familiar in their own cultures.   They did so in the similar manner many people today falsely say nirvana is Buddhist heaven (actually it's freedom from rebirth, nonexistence) and thus represents a terrible misconception.   

One way that happened was due to people associating fertility gods like Baal and Cromm, and then taking the Celtic holiday of Beltane and saying it was a festival to Baal (false etymology), in sharing falsely made linguistic roots and then saying Baal was actually another name for the biblical Satan (which is not true even biblically).   And as the devil to Judeo-Christians (influenced by Greek mystery cults with resurrection myths and concept of Tartarus as a place of punishment for wrongdoing with its lord Hades who tortured) was culturally created by Jesus' times, Baal became conflated with the devil who theologically was lord of the underworld, hell, of the Judeo Christian afterlife.  Early Jews, Egyptians, and Greeks had no concept of hell, and only a concept of the afterlife or death and underworld, the place where both the righteous and unrighteous went.  But by the Hellenistic Greek period, Hades had evolved to include a place of reward in the Elysian Fields and place of punishment in Hades, and the same thing happened within Judaism and within Egytian mythology.    

The Egyptian analogue of the Celtic Cromm would have been Osiris; the Greek, Hades; the Roman, Pluto; and the Sumerian, Nergal or Moloch both similarly derivative from Baal in the same way Cromm was derivative of Dagda, and Baal of El.   And so the logic of these scholars was to group the fertility gods and gods of the underworld then presuppose common origins in Indo European belief and was inductive in nature.  They started from a premise, and sought evidence for their foregone conclusions, leading them to miss the nuance that in no way was Cromm actually derivative of Baal and they never in reality had any real or imagined relationship whatsoever.     

The claim that Baal was the chief God of the Celts is flatly erroneous but still circulates today, especially in Christian sources. Ruth E. Kelley's seminal 1919 The Book of Halloween, the first book published on Halloween history, is one major source of this falsehood.  Baal was not—as not one single Celtic deity is mentioned in the Holy Bible—the chief god of the Celts, nor was he ever.  Thus this misunderstanding appears to derive from association of Baal, the Sumerian god of fertility, weather, and rainstorms (the son of their over god El), with the Sumerian god of the underworld Nergal in associating Cromm and Baal in both being fertility gods to whom sacrifices were made, irrespective that Baal was never an underworld god, and the false etymological linguistic (word origins) attempts to trace cosmologies from early proto-Indo-European people to the Celts.

Today, most scholars recognize that Baal is in no way remotely related to Cromm other than the fact they are both fertility Gods.  But neither El nor Baal were ever gods of the underworld like Cromm was.   Cromm got infected with the stigma of Baal because he had the misfortune of being a fertility god like Baal, and Baal had become associated with Satan/the devil.  It's a case of guilt by false association, false etymology, and sloppy ethnocentric scholarship.

It was also likely influenced by projection and conflation by Christians of the devil or Lucifer in hell with the underworld.  The chief god of the Irish Celtic pantheon was always and has always been Dagda, the "good god," or chief over god of life and death (and of seasons, agriculture, fertility, and magic).  Cromm over the centuries evolved to replace aspects of Dagda as the god of seasons, agriculture, fertility, and magic, a necessary scapegoat like Lucifer evolved to become in the adversary biblically.   But in reality, Lugh was the Celtic sun god like either Roman Sol or Greek Apollo, and Cromm the Celtic analog to the Greek Hades or Finnish Tuoni.  There definitely were analogs in Indo-European and Finnic-Ugric peoples, the ancestors of all Europeans, but not all associations made by scholars were accurate.  

But to group fertility gods and then take a function of one who also was associated with death as well as fertility and then equate the same to evil because hell was conceived of as being literally under the ground just like the Celtic underworld (likely inferred from hot springs and geothermal locations, enhancing imagery of hell as the midden burning pit of Sheol outside Jerusalem) was how people have unfortunately long incorrectly equated Cromm with the lord of hell Satan (by the 16th Century, Baal was strongly associated with Satan by the Roman Catholic Christians).  

Thus, in the same way Westerners tried to convey the meaning of Buddhist nirvana to mean Buddhist heaven because it was a more familiar analogue, sources by the 1600s dedicated to these topics equated the Greek Hades, the Sumerian Baal, the Egyptian Osiris, and the Celtic Cromm and they were all used loosely and interchangeably by the Protestant Reformation to be synonymous with Beelzebub (the Lord  of the Flies) and synonymous names for the devil. Because the underworld was underground below us (and heaven above us), all gods of the underworld in all cultures became to be seen as different names of Satan, the deceiver, who appeared to different people as different counterfeit deities instead of the one true god of El/Yahweh. Hades was just the Greek name for Lucifer, as Cromm was to the Celts it seemed.  But these interpretations were vastly polluted by Christian emotional baggage.       

Transliteration of the king of hell Bael mentioned in mid-17th Century (1600s) demonological grimoires is likely a corruption of Baal.  In those sources, this king's name is alternately spelled Baal (also Baall or Boel),   suggesting the hoarse-voiced king of hell who appears as a man, toad, or cat (imbuing the power of invisibility and commanding sixty-six legions of demons) had been by then equated by Christians with Satan, Lucifer, and Beelzebub.  This suggests the equation of Baal with all things Satanic was complete by the start of the Enlightenment and Age of Reason, and poor Cromm just had the bad luck of being wrongly implicated as Baal's Celtic analogue.