"A different version of Medb's relationship with Fergus is found in the obscure poem Conailla Medb míchuru ('Medb has entered evil contracts') by Luccreth moccu Chiara (c. 600); it asserts that Medb wrongly seduced Fergus into turning against Ulster 'because he preferred the buttocks of a woman to his own people.'"

-- Wikipedia article on Medb