One of the great heroes of Irish mythology, usually known as the Hound of Ulster. First called Setanta, he did not win his name Cuchulainn, until he slew a huge ferocious hound at the age of 7 with his bare hands. The hound was guarding the royal party of King Cochobar Mac Nessa while Culann, a wealthy smith, was entertaining them. Culann was so upset by the loss of his great hound that Cuchulainn offered to take its place. The offer was declined but thereafter he was known as Cuchulainn (the Hound of Culann)

His powers as a fighting machine were awesome. Before going into combat he went though a transformation known as ríastrad (battle frenzy); his body quivered violently; his heels and calves appeared in front, and his feet and knees to the back; one eye receded into his head and the other huge and red on his cheek; his mouth met his ears and foam poured out of his jaws. The muscles on his neck stood out like the head of a baby. The beats of his heart sounded like the roar of a lion and from the top of his head, a column of blood that scattered in all directions formed a mist of gloom. When a horn, the size of a man's fist projected through the top of his head, he would be ready to fight. In battle he would surprise his enemies when he pounced on them with a huge leap.
To calm him from his battle fury, the Ulster Queen Mugain once sent 150 naked women carrying three vats of iced water. The embarrassed Cuchulainn was quickly put into the vats; the first one burst, the second boiled, and the third warmed.
Acclaimed as the champion of Ireland in a beheading! contest; he was unbeatable and his skill was needed in his most famous campaign as told in the story of 'the Cattle raid of Cooley', where Cuchulainn single-handedly defended Ulster against Connacht's Queen Madb.