[1] In the saga "The Siege of Howth", he goes on a circuit of Ireland, visiting kings' courts, and making outrageous demands of hospitality, knowing that disgrace would fall on any kingdom that refused him, and that if anything happened to him the Ulstermen are bound to go to war in his defence.
In the ensuing pursuit, the Ulster hero Conall Cernach kills Mesgegra in single combat and takes his head.
[2] When Amergin, son of Eccet Sálach the smith, who has lived to the age of fourteen without speaking, suddenly utters a cryptic poem, Athirne fears the boy will replace him as chief poet of Ulster, and resolves to kill him with an axe.
She dies of shame, and Athirne and his sons flee to his house on the hill of Benn Athirni on the River Boyne, fearing Conchobar's vengeance.
Conchobar gathers the heroes of Ulster, walls him in and burns the house down, killing Athirne, his sons, and his two daughters Mór and Midseng.