William Corvinus is the first and only Lycan Elder in the Underworld mythos. He is the son of the first immortal and was bitten by a wolf, thus turning him into a Lycan. He is played by Brian Steele.
William was the son of Alexander Corvinus and the twin brother of Marcus Corvinus. Both were born sometime in the 5th century. He, along with Marcus, inherited the immortality strain from his father. Marcus and William shared a bond that Alexander never truly saw. Marcus was bitten by a bat and William by a wolf. He thus became the first true Lycan. Unlike later Lycans, he was an albino Lycan and could not transform back to human form. His lycanthropy virus was much more infectious than Marcus' Vampire virus, even allowing dead victims to transform.
In 1202, he was captured by Marcus' vampiric Death Dealers just after he infected an entire village. Against Marcus' wishes, William was imprisoned by Viktor in his fortress, far from Marcus' reach. This caused Marcus to swear vengeance against Viktor and those loyal to him.
Centuries later, William was freed from his dungeon by Marcus. Their bond still remained strong to the point that William recognized Marcus even through his own bestial nature. William proved to be a powerful creature, despite his centuries of confinement with no blood to feed on. He infected the Cleaners who came to fight him and also battled the hybrid Michael Corvin, descendant of his mortal brother, absorbing immense amounts of damage with no obvious signs of trauma done to him. The centuries of bloodless confinement, however, still left William significantly weaker than he once was. Because of this, he was unable to defeat the powerful hybrid, Michael, who tore apart the Lycan Elder's head with his bare hands. Though, it could also be argued that Michael had just been resurrected from death without the absorbence of blood, making him weaker than normal, as well as evening the playing field between him and William. In the end, Michael was just the better fighter that night.