The Old World Wizard appears to be a wiry human but has pale grey skin. On his forehead is a tattoo of an Old World symbol. When first encountered he wore the blue robe and pants of the Brothers of the Old World. After his death and return he had severe scars reflecting his death wounds, visible because he was naked to the waist though he still wore the pants and red bracelets.
The Old World Wizard does not speak when casting but appears to have cast four spells, including spells equivalent to Mirdon's explosio, lightning and power beam. He can return from the dead. He commands the loyalty of the Brothers of the Old World and of the megafists, and presumably wealth sufficient to hire Giligorf.
When he fought Mirdon with power beam, Mirdon said he was very strong and that Mirdon would not be able to match him for long. Also, he described serpentes limbus, one of Mirdon's more powerful spells, as "simple magic". This suggests he is the most powerful and skilful wizard seen so far.
The Old World Wizard is first encountered in Dongo leading a conspiracy called the Brothers of the Old World. He threatened to kill Doraleous but was instead killed by the Associates. All his men were killed by Mirdon and Sir Walken before he returned to life and attacked Doraleous. He was defeated and killed by the joint efforts of Doraleous and Associates.
Later, alongside other Brothers of the Old World he plotted to open a tranny hole to allow the megafists to enter Nudonia, bypassing Nudonia's defences at the Gate to the Old World. In this he followed a vision of Lord Lazzerzazzerzazzerzazzer (about whom nothing else is known). His main objective was to free Barat from Arzon Prison, then support Barat in conquering Nudonia. He is killed by Doraleous.
"On a scale of one to ten, how Doraleous are you?"