Eochaid gave Conchobar another of his daughters, Eithne (or Clothru),[14] but Medb murdered her while she was pregnant; her son Furbaide was born by posthumous caesarian section.

[17][18] Medb insisted that she be equal in wealth with her husband, and started the Cattle Raid of Cooley when she discovered that Ailill was one powerful stud bull richer than her.

She discovered that the only rival to Ailill's bull, Finnbennach, was Donn Cúailnge, owned by Dáire mac Fiachna, a vassal of Conchobar's.

But when a drunken messenger declared that, if he had not agreed, the bull would have been taken by force, Dáire withdrew his consent, and Medb prepared for war.

[20] Because of a divine curse on the Ulstermen, the invasion was opposed only by the teenage Ulster hero Cúchulainn, who held up the army's advance by demanding single combat at fords.

Medb and Ailill offered their daughter Findabair in marriage to a series of heroes as payment for fighting Cúchulainn, but all were defeated.

Examples of this occur when Cúchulainn "slung a stone and killed a pet stoat as it sat on Medb's shoulder by her neck, south of the ford.

[21] Medb's behaviour further illustrates the importance of the landscape when she goes to great lengths to permanently alter it to show her contempt for Ulster.

"She preferred to cross the mountain by leaving a track that would show forever her contempt for Ulster… to make the Pass of the Cualinge Cattle".

[23] In his old age, after Conchobar's death, the Ulster hero Conall Cernach came to stay with Ailill and Medb, as they were the only household capable of supporting him.

[14] According to legend, Medb is buried in Miosgán Médhbh, a 40-foot (12 m) high stone cairn on the summit of Knocknarea (Cnoc na Ré in Irish) in County Sligo.

Her home in Rathcroghan, County Roscommon is also a potential burial site, with a long low slab named 'Misgaun Medb' being given as the most likely location.

Tomás Ó Máille was the first to suggest in 1928, that Medb is probably an allegorical figure representing the sovereignty of Connacht,[24][25] "whom a king would ritually marry as part of his inauguration.

[27][28] Her name is said to mean 'she who intoxicates', and is cognate with the English word 'mead'; it is likely that the sacred marriage ceremony between the king and the goddess would involve a shared drink.

Medb's "pillow talk" argument with her consort contains suggestions of matrilineality, as does Ailill's taking his name from his mother Máta Muirisc.