In the second verse of Preiddeu Annwfn , the bardic poem which appears to have initially given rise to the characters of Pwyll and Pryderi, we find the following lines:
The Cauldron of the Head of Annwfn: what is its faculty?
Dark-blue and pearls around its rim
It will not boil the food of a coward: it has not been so destined
Here we find the earliest known reference to the figure of Pen Annwn (or Pen Annwfn to use the correct Middle Welsh orthography). The archetype, if not the name, seems to have a considerable antiquity in the magical thinking of the British Celts. It was this archetype that seems to have quickly subsumed the nascent patronymic Pwyll, resulting in the creation of a composite character: Pwyll Pen Annwfn, who was to play a leading role in the First Branch of the Mabinogi. First, however, we should consider the profile of the otherwise unnamed Pen Annwfn - a more generic figure who appears in the Preiddeu Annwfn simply under that title. And in his capacity as Head of Annwfn and The Bearer of the Cauldron he seems to have assumed the mantle of constellations already familiar to the Celtic imagination, with a number of archetypal antecedents. Annwfn, as we have seen, was the Indigenous Underworld par excellance of the British Celtic tradition. It was associated in folklore with the ‘Hollow Hills’ motif: that is the faery underworld accessed through tumuli and other similar numinous points on the megalithic sacred landscape. It had numerous parallels with the Irish tradition of the sídhe, identified in some sources with the indigenous, pre-Celtic population.
The primary meaning of the Welsh word pen is the physical head of a living being, or the summit of a hill or other pointed object. However, as in many other languages (including modern English) it carries the secondary meaning of chief or leader of a human organisational ‘body’, whether this be a family grouping, a military unit or a municipal/political corporation. But this word might be expected to have carried additional significance in the Celtic world by virtue of the certain popular fantastical motif we shall refer to as The Living Head. As well as playing a prominent role in the Second Branch, the archetype of a disembodied head which maintains the ability to speak, sing, entertain, curse or exercise protective magic frequently appears in the medieval literature and oral folk-traditions of the Celtic World. There is every suggestion that this motif has its roots in the magical thinking of the pagan Celtic world. It seems possible that the archetype of Pen Annwn, with which the name of Pwyll became subsequently associated, may have had its origins in a narrative tradition of this kind. Whether or not the archetype of the Living Head would have been associated with the pen Annwn remains an open question. But there are a number of other characteristics that can be associated with the Pen Annwn with a greater degree of certainty. The first of these is the possession or guardianship of a mysterious cauldron, simply known as Peir Pen Annwfn, as described in the lines of verse above.
The Cauldron was a numinous symbol in the Insular Celtic mythos, closely related to the Goddess and the bounties of nature. But it was also frequently to be found under the guardianship of a tutelary god, with strongly sovereign, chthonic associations. In the Irish tradition, the guardian of the cauldron is simply known as Ind Dagda, ‘The Good God’. He is characterised by a primitive, phallic demeanour: his crude and violent copulations with the dark goddess Mórrigan being responsible in one story for shaping some of the plains, ridges and earthworks of Ireland. His belly and appetite were vast, and his garb was that of the stone-age peasant: a course brown tunic from which his buttocks protruded. In Gaulish iconography, we find a similar god known as Sucellos ‘Good Striker’ whose elemental hammer was undoubtedly associated with the virtues of thunder and lightening, while his bowl, carried in the other hand, signalled (like the cauldron of Dagda) his mastery of the bounty of nature (i.e. his conjugal relation to the Great Goddess). The Arthurian counterpart of this archetype is to be found in the Grail King, whose health and vitality is mysteriously linked to the state of the land. It would seem that the cauldron in question was representative of this mythic constellation: and we might therefore reasonably conclude that the Pen Annwfn was closely related to the archetype we have called the Cauldron God: earthy, phallic, often giant in proportion and associated with the material well-being of his tribe. The name Pen Annwfn would also suggest links to the megalithic underworld. Aspiring Celtic kings would, in one way or another, have to deal with the figure of the Cauldron God and his female counterpart, the Goddess of Sovereignty (of her, more will be discussed below), as part of their acceptance into the mysteries of kingship. Thus we find this figure recurring in Celtic myth in the role of the initiator: helpful and avuncular at one moment, eerily malevolent and duplicitous the next. His role is to test the would-be king, breaking those who are unworthy and rewarding the righteous with the cup of Sovereignty.
As well as the Cauldron God, Pen Annwn was also the magical king of the Indigenous Underworld. Another representative of this aspect in the Welsh tradition was the famous Gwyn ap Nudd, a deeply-rooted figure in the Insular Celtic world with strongly pagan (even diabolic) associations. He is described in one late source as brenhin annwn, King of Annwfn, tempter and adversary of the sixth century West Country British hermit, St. Collen. Here he is associated with Glastonbury Tor and ‘The Land of Summer’. Like Arawn, he is engaged in a perennial conflict ‘at the calends of May’ with a rival lover of his mistress Creiddylad daughter of Llud Silver-Hand. He has the ability to conjure a splendid feast from little more than grass and leaves. He also bears many of the hallmarks of his savage, pre-Christian background: he leads the ‘wild-hunt’ - a pan-European pagan tradition of a riotous chase across stormy skies by the horse-borne god of the dead and his magical hounds. In the early Arthurian folktale of Culwch and Olwen, we are told that in Gwynn ap Nudd ‘God had set the spirit of the demons of Annwn, lest the world be destroyed’. Later on in that story he is described as forcing an enemy to eat his own father’s heart. The tradition of Gwyn, it might be suggested, represents a parallel to that of the pen Annwn, and one which sheds considerable light on the constituency of this mysterious archetype. His was quite probably a powerful and enduring pagan cultus: hence his demonisation at the hands of the medieval clerical-bardic authors. Yet behind this daemonic, and in some ways misleading, facade there are further suggestions of a deep-rooted connection between the faery realms of the Indigenous Underworld and the pre-Christian concept of an animistic, ancestral presence immanent within the natural world.
So the Pen Annwn is probably best understood as the representation of a pagan British deity who enacts the roles both the magical lord of the Indigenous Underworld, and the ancestral guardian of the mysterious rights of sovereignty over the world of nature. The Pen Annwn would have ruled the ancestral spirits which, in the indigenous megalithic past, would have been invoked and placated at the gateways of their tumuli in order to guarantee the continuance of fertility, the smooth running of the seasons and the protection of the tribe from famine and disease. It was this magical power which, at some stage, had to be wrested by the incoming, proto-Celtic post-megalithic peoples, from whom the medieval audience would have claimed their descent. Dyfed, it would seem, was one of the final inheritors of this megalithic connection. It is therefore perhaps not surprising to find, in the Mabinogi of Pwyll, that it was a Demetian king who was assigned the mantle of the Pen Annwfn in this medieval history of the British tribal fore-time.
There is a probable connection between the name of Annw(f)n and the andedion, the 'under gods' mentioned in the Gallo-Brittonic magical inscription at Chamalières in the Auverne in central France. A further connection may be noted with the cognate andée described in the Lebor Gabala as the farmers and husbandmen of the gods. All of this is described in appendix of my study of the The Four Branches of the Mabinogi (2005), in which a systematic survey of what little we know about the religious systems of pre-Christian Celtic Britain has been undertaken.