In the Ulster Cycle

Ulster Cycle

The Ulster Cycle , formerly known as the Red Branch Cycle, one of the four great cycles of Irish mythology, is a body of medieval Irish heroic legends and sagas of the traditional heroes of the Ulaid in what is now eastern Ulster and northern Leinster, particularly counties Armagh, Down and...

 of Irish mythology

Irish mythology

The mythology of pre-Christian Ireland did not entirely survive the conversion to Christianity, but much of it was preserved, shorn of its religious meanings, in medieval Irish literature, which represents the most extensive and best preserved of all the branch and the Historical Cycle. There are...

, Finnbhennach ("white-horned" sometimes rendered as "Whitehorn") was an extremely fertile stud

Stud (animal)

A stud animal is a registered animal retained for breeding. The terms for the male of a given animal species usually imply that the animal is entire—that is, not castrated—and therefore capable of siring offspring...

 bull

Bull

Bull usually refers to an uncastrated adult male bovine.Bull may also refer to:-Entertainment:* Bull , an original show on the TNT Network* "Bull" , an episode of television series CSI: Crime Scene Investigation...

 owned by king Ailill

Ailill mac Máta

Ailill mac Máta is the king of the Connachta and the husband of queen Medb in the Ulster Cycle of Irish mythology. He rules from Cruachan .-Family background, marriage and offspring:...

 of Connacht

Connacht

Connacht , formerly anglicised as Connaught, is one of the Provinces of Ireland situated in the west of Ireland. In Ancient Ireland, it was one of the fifths ruled by a "king of over-kings" . Following the Norman invasion of Ireland, the ancient kingdoms were shired into a number of counties for...

.

He was originally one of Bodb Dearg's pig-keepers, who fell out with one of his colleagues. The two fought, taking a series of animal and human forms, before finally becoming two worms who were swallowed by two cows and reborn as two bulls, Finnbhennach and Donn Cuailnge

Donn Cuailnge

In the Ulster Cycle of Irish mythology Donn Cúailnge, the Brown Bull of Cooley, was an extremely fertile stud bull over whom the Táin Bó Cúailnge was fought....

. Finnbhennach was born into the herds of queen Medb

Medb

Medb – Middle Irish: Meḋḃ, Meaḋḃ; early modern Irish: Meadhbh ; reformed modern Irish Méabh, Medbh; sometimes Anglicised Maeve, Maev or Maive – is queen of Connacht in the Ulster Cycle of Irish mythology...

, but thought belonging to a woman beneath him and joined her husband's herds instead.

Donn Cuailnge was born into the herds of Dáire mac Fiachna

Dáire mac Fiachna

In the Ulster Cycle of Irish mythology, Dáire mac Fiachna was an Ulster cattle-lord and owner of Donn Cuailnge, the Brown Bull of Cooley, over which the Táin Bó Cuailnge was fought....

 of Cooley. He bulled a heifer belonging to the Mórrígan

Morrígan

The Morrígan or Mórrígan , also written as Morrígu or in the plural as Morrígna, and spelt Morríghan or Mór-Ríoghain in Modern Irish, is a figure from Irish mythology who appears to have once been a goddess, although she is not explicitly referred to as such in the texts.The Morrigan is a goddess...

, and the resulting bull-calf fought Finnbhennach, and narrowly lost. After seeing that Medb was determined to see Finnbhennach fight the bull-calf's sire.

When Medb discovered that owning Finnbhennach made Ailill richer than her, she resolved to even the account by possessing Donn Cuailnge. She launched the Táin Bó Cuailnge

Táin Bó Cúailnge

is a legendary tale from early Irish literature, often considered an epic, although it is written primarily in prose rather than verse. It tells of a war against Ulster by the Connacht queen Medb and her husband Ailill, who intend to steal the stud bull Donn Cuailnge, opposed only by the teenage...

(Cattle Raid of Cooley) and eventually brought Donn back to Cruachan. The two bulls fought. Finnbhennach was killed, Donn Cuailnge mortally wounded.