The Skull Knight is one of the most mysterious and prolific characters introduced in Berserk, a towering warrior dressed in full armor whose ornaments, especially his helmet, are shaped as parts of a human skeleton, hence his moniker, who rides a massive, ghostly black horse. Though ominous and macabre, he is an enemy of the Godhand and its acolytes, hunting down Apostles and devouring their Behelits; especially bitter is his rivalry with Zodd the Immortal, whom he was often showed to overwhelm with ease.
He wields a powerful sword that, when stuck down his throat, becomes a terrible, Behelit-coated blade capable of slashing rifts through reality itself, thus allowing the Skull Knight to move freely around the world or even between different dimensions.
This enigmatic knight saved Guts in more than one occasion, notably during the infamous Eclipse which saw Griffith become a member of the Hand of God or when Slan almost slaughtered him, though he never explained why, simply declaring that the Struggler (the way he calls Guts) has to keep following his fate.
During his life as a mortal, the Skull Knight was in fact Gaiseric, the warlord that unified the Midland and became its first Emperor, notorious for his helmet whose shape was that of a human skull and whose ambitions 'prompted God to send four Angels' (most likely the four members of the Hand of God) to punish him.
He was the wearer of the Berserker's Armor, and knew the witch Flora. During the duel between Griffith and Ganishka he suddenly appeared out of thin air through a dimensional rift, trying to land a fatal blow on the Hawk, only to see it diverted on the writhing body of the Kushan Emperor.
The knight is your traditional hero, fighting against monsters and wicked men to save kingdoms from evil. Legends of these heroes have persisted over the centuries and we continue to make new ones today.