Earth magic is awesome! There are so many good spells! Although Fire magic is also great. And Geksorin was right about the Berserk spell. I recently won a game against the AI on Champion difficulty thanks to the Berserk spell (I cast it on 4 units at once), otherwise I would have lost. But none of the magic types are unbeatable if you have the Spell of Disruption! My friend once maxed out all four magic types to Expert level, and then someone came along with the Spell of Disruption! He was so disappointed!