Chaos magic. Is it necessary?

I don't know, I mainly play with Warrior heroes, not mages. So, for Haven, it's a good skill, and moreover, the heroes of the Haven faction are mostly Warriors; only 2 heroes have basic skills (Light and Summoning). All the others have different skills. My choice is for the Warrior; Chaos is needed, in my opinion, but in small amounts and not for all heroes.