Son of Lug, Cuchulainn began life with the name Setanta, but after
he had killed Conchobair Mac Neasa's favourite guard dog, after it had
attacked him, he vowed to take the place of the dog, guarding the pass
into Ulster, and thus became known as the Hound of Cualainn.
Cuchulainn' s great heroic strength was mostly due to his 'warp
spasm', a violent, unnatural occurence that channeled the power of
Danu, the earth goddess, through his body, twisting and contorting his
body into impossible shapes:his heels and calves stood out in
front, one eye receded into his head, the other hung huge and red on his
cheek. His hair bristled like spikes, with a drop of blood on the tip
of each hair-spike, and from the top of his head arose a thick column
of dark blood, that spouted like a geyser from his head.
While the Men of Ulster were 'in their pangs', Cuchulainn held the
pass into Ulster against hundreds of fighters, with the condition that
only one man per day should come against them. All who fought him he
slew, but he almost met his match in his brother Ferdia, and the two
heroes fought for days before Ferdia was finally defeated, Cuchulainn
himself the worse for the wear.