|It's a blast.
Background: Vonotar was a member of the wizards' guild of Toran but he betrayed them for the magical power of the Darklords' wizards. He then ends up in Kalte, controlling the mind of the ice barbarian chieftain. You catch him and Vonotar is thrown into the shadow gate which leads to another dimension. You also get thrown into the shadow gate a few years later where you come across him again. And he's annoyed.
Prominence: Vonotar or his servants are not prominent in any of the books, but he is one of the few recurring gamebook villains. Bonus marks for this. 6/10.
Hardness: With a power ring he wields, Vonotar has a combat skill of 30 and an endurence of 21. He is immune to Psi surge and mindblast. His endurance is quite low, but his combat skill is quite high for an ordinary wizard (I expect the power ring improves it). He also manages to blast you and damage you for five endurence points before the combat and before you get near to him, you have to fight five notorious criminals from Sommerlund which have a combat skill of 38 and and endurance of 46 together. Killing him and the five criminals is a pretty tough job even with all of the combat skill raising weapons and skills you have. 7/10.
Ambition: Vonotar's orginal ambition is more magical power, but then he tries to take over ice barbarian tribes. His ambition in the Prisoners of Time is to get home. Ultimately, Vonotar is a lackey to the Darklords and so can't get too high a score in ambition. 4/10
Style: Quite typical wizard with a typical modus operandi of wizards. 4/10
Diabolical genius: He manages to get the Kai Lords killed but after his initial betrayal, his genius kind of stops there. 4/10
Total score: When it comes to Lone Wolf's enemies, Vonotar is a small fish that resurfaces more than once. 25/50.