Manannan mac Lir

In Celtic mythology, Manannan mac Lir was a sea and weather god. He was one of the Tuatha de Danaan, though he was considered older than them. His parents were Lir and Penarddun and his wife was Fand. He ruled over the Blessed Isles as well as Mag Mell, the underworld.

Manannan had many magical items. He gave Cormac his magic goblet of truth; he had a ship that did not need sails; he owned a cloak that granted him invisibility; a flaming helmet; and a sword that could never miss its target.

Manannan left his wife, Fand, and she fell in love with Cuchulainn. Since a mortal and fairy (Fand was Queen of the fairies) could not stay together without destroying the fairy, Manannan erased their memories of each other.

He raised many foster children:

In the Isle of Man, Manannan mac Lir was known as Mannan. On Midsummer Eve, people offered green grass to Mannan-beg-mac-y-Leir and prayed for blessings in seafaring and fishing. He was believed to be a magician who could make an illusory fleet from pea shells in order to discourage would-be invaders.

Alternative: Manawyddan ap Llyr (Welsh), Barinthus, Manannan, Manawydan, Mannan (Manx)