Which hero do you like?

If you're to be believed, then the Wizard should often get spells of the Haven faction! Specialized magic is like a library that exists in the city!

You misunderstood me. For successful development of Demonology, the Necromancer must have Nature magic, so the chance of it appearing for a Necromancer is slightly higher than the chance of a Wizard getting Haven magic (I didn't calculate it specifically, but IMHO it appears more often). :)