Dictionary of Celtic Myth and Legend;

Warlike, exuberant and superstitious, the ancient Celts saw divinities in every facet of life and nature, venerating deities of the sun, thunder, water, war, healing, hunting, fertility and death. They possessed a complicated array of concepts and rituals, a powerful priesthood - the Druids - and a pantheon which included the goddess-queen Medb and the Morrigan, a sinister war-goddess.