Flaws that help in the game...

I don't know if it's a bug or an intentional feature. Anyway, on the "War for Survival" map, there are succubi near a suspension bridge, and if you attack them with a secondary hero who has only one level 1 creature, they will join your faction. I've tested it five times, and they always joined.
P.S.: This is good news for Necropolis and Inferno players.