|Eschatology is the end of time in a religious system. Celtic eschatology is not "linear" but cyclical, like the Hindu and Teutonic cycles of time. The Teutons believed in Ragnorok, which would mark the ending of this age. The world would be destroyed by fire and ice, the gods and giants would fight it out and the world would be reborn in a new creation. Hinduism teaches of kalpa, in which a new beginning will similarly come after the destruction of the cosmos.)
A belief that fire and water would destroy the manifested world was also preserved by the ancient Druids. Strabo wrote of such a doctrine being preached by Gaulish Druids. This idea is Indo-European in origin and is probably the source of the Christian doctrine of humanity’s resurrection on the Day of Doom. To the Celts, though, death was the end of the manifested body and integrated form; the entrance of the transcendent spirit to the Upperworld and the non-transcendent shadow to the Underworld. One’s own living soul went to his other descendants, or the descendants of his or her relatives, to be reborn. The "shadow" was the ghost, púca (spook, shadow) or taibhse which could haunt places, and the Celtic explanation for poltergeists and hauntings. The shadow could also take on a bodily shape.
It is taking control of the púca and anatios/anatia (spirit) that we call self-transformational magic: the highest form of magic, the magic of self-discipline.