Linked to the conception of Donn Cuailnge [the Brown Bull of Cooley] in a strange story. One day while he was fishing in Cuailnge, Fiachna caught a ‘water worm’ who spoke, telling him that a great fight would come with the beast of Connacht. Another water worm, found elsewhere in a river at the same time, advised Queen Medb of Connacht to marry Ailill, who did indeed become her husband. Both worms were then swallowed by two different cows, who subsequently gave birth to the famous bulls, the worm advising Medb anticipating the white bull of Connacht, Finnbennach, and Fiachna's worm anticipating Donn Cuailnge. See also DÁIRE MAC FIACHNA whose refusal to surrender Donn Cuailnge prompts Medb's aggression against Ulster in Táin Bó Cuailnge [Cattle Raid of Cooley].