Patron of sheep and cattle, Bel's festival is Beltane, one of two main Celtic fire festivals. Beltane celebrates the return of life and fertility to the world -- marking the beginning of Summer and the growing season. Taking place on April 30, Beltane also is sometimes referred to as "Cetsamhain" which means "opposite Samhain." The word "Beltaine" literally means "bright" or "brilliant fire," and refers to the bonfire lit by a presiding Druid in honor of Bile.
"Some believe this deity is the equivalent of Belatucadros, the consort of Belisama, another patroness of light, fire, the forge and crafts. Belatucadros, whose name means "fair shining one" or possibly "the fair slayer," is the god of destruction and war and transports the dead to Danu's "divine waters." Celtic deities often reign over seemingly contradictory themes. In the case of Belatucadros, death was simply a pathway to rebirth in the Otherworld, thus linking the two themes together. However, according to Ross's Pagan Celtic Britain, historically the worship of Belatucadros among the Celts was confined only the northwestern region of Britain and has never been associated with the festival of Beltane, healing or with a consort (pg. 235).
It has been suggested that the mythological king, Beli Mawr, in the story of Lludd and Llefelys in The Mabinogion, is a folk memory of this god. In Irish mythology, the great undertakings of the Tuatha Dé Danann and the Milesians -- the original supernatural inhabitants of Eiru and their human conquerors, respectively -- began at Beltane. The Milesians were led by Amairgen, son of Mil, in folklore reputed to be the first Druid.