The "Diplomat" scenario.

If you've played this before, you should know how to act. Stock up on Earth and Mind magic. "Plague" and "Confusion" are essential, as is "Resurrection." Turn all peasants into archers. Get rid of the griffins. Have more paladins and angels.
Don't let this mage catch you. Have a couple of heroes distract him so he chases them.
You know where to lead your hero.