Warlock – “Expansion” [4th campaign, 2nd mission]

Besides, with a greater number of Sylvan factions in this campaign than Inferno, the probability of casting chaos and dark magic spells is significantly reduced.

Spells can also be learned in neutral buildings such as pyramids and mage repositories. I had Agrael as a master of dark magic and he knew Blind (I don't remember where he learned it), not to mention mass slow and confusion, which are available in most castles. However, I didn't manage to max out his special ability, although I leveled him up to 31 (in the last mission), because from around level 27, I was persistently offered some useless skills, and I had to level up his machine control.