"Versago" is a mistranslation (probably deliberate) of the name Vassago. In demonology, Vassago is a mighty Prince of Hell, ruling over twenty-six legions of demons. He can be persuaded to tell the magician of events past and future, can discover hidden and lost things, and has a "good" nature.
Vassago is specifically the Prince of the Southern Regions of Hell. He is said to be the Demon of Prophecy and the controller of the element enchantment air and Air Elementals (air demons).
Vassago is a relatively calm demon and usually remains quite mellow and quiet and kind, though in combat he can be fast and fierce. He is a lover of magic.