New units. Their discussion and selection of upgrades.

Immunity to earth is useless. Warlocks don't care about immunity anyway, as their Undead creatures are already immune. Mages might not even get the Shock spell, and even if they do, it's questionable whether they'll use it. Elves fighting elves is a rare occurrence. And demons, with their inherent resistance, are also immune to Shock. So, it seems like this immunity is just for show.