Xebinon was an Archmage and Daemonist that was since trapped by a demon of the 10th Circle in his mannor.
It is said that Xebinon used the Crown of Hellfires to try to tame the Arch-daemon (and failed) - this is a crown that gave a lot of power, but drained the magical force of the wearer at the same time, making the spell regeneration more difficult. This was in fact a cursed, twisted artifact, created by daemons for people who were seeking short-term power, but would thus head directly for long-term soul slavery.
Xebinon is sometimes called “The faceless one”, as it is said that the daemon trapped him by stealing his visage. This may explain why magical artifacts wearing his name are often helmets.