Samhain was an ancient Celtic festival, known in modern times as Halloween, marking the start of winter and the ascendance of the powers of blight, decay and death. It was the boundary between one year and the next, and so double magickal. At Samhain the material and spiritual world unite. After Samhain, ghosts, spirits and evil fairies walk the land. Good fairies, such as the Irish Tuatha Dé Danaan and the English Puck, retire from sight until spring returns. Wicked fairies, such as the Scottish Unseelie Court, become very active from now until Easter. Evil omens, such as black dogs and the Bean-Nighe or Washer at the Ford, also appears.

After Samhain all the crops left unharvested belong to the fairies. In Ireland, Halloween is called Phooka Night and after this time he renders all the crops unfit to eat and spoils all the blackberries. Welsh gryphons blight any crops left in the field after Halloween and the Lunatishee will now allow Blackthorn to be cut on November 11th (Old Samhain before calendar changes).

In Scotland, the Cailleach Bheur ('Blue Hag') strides across the land, beating down the vegetation with her staff and hardening the earth with frost. When her season has fully set in, she brings the snow. As spring approaches, her power begins to wane, until at Beltane (May Day) she gives up her struggle, flinging her staff under a holly tree, and this is why no grass can grow there. She then shrinks to a grey stone to wait until her season comes again. It is said that if anyone can find her staff, he or she will have the power of destiny over the human race.

She is a folk survival of a winter crone goddess, reborn each Samhain the start of winter, and proceeds to blight the Earth with snow and cold. She has two sons, one black and the other white. Each year one of them will steal the single eye and chase her north, before marrying the Summer Maid. She is one of a number of hag or crone fairies. Another is the Polish Marzanna, who is the personification of winter, a hag of death. Every spring, an effigy of Marzanna, together with her broom, was "drowned" to symbolize the end of winter and return of spring.