In the First Battle of Mag Tuireadh, King Nuada of the Tuatha de Danaan lost his hand; because he was imperfect, he could not be king. Hoping to reconcile relations between the Fomorians and the Tuatha de, Bres was named king and the Tuatha de, Brigid, married him.
Bren raised taxes and made the Tuatha de work as slaves. Nuada had his hand replaced by a superior, silver one and Bres was exiled. He led the Fomorians in the Second Battle of Mag Tuireadh but lost. He was not killed because he promised to teach the Tuatha de agriculture.