Dark Elves vs. Mages.

Teaching Chaos against Mages is one of the biggest mistakes you can make. The only thing worse is teaching Darkness against Undead without Sandro's cloak. So, of course, we summon a Phoenix and beat up the Golems.
Yes, elemental balance is dangerous. Well, if its probability is high, you can sacrifice a bit of development for Chaos -> Deadly Cold in addition to summoning.