Walkthrough for the "Tribes of the East" expansion.

I don't understand... I assembled an army, transformed everyone into Necromancers, and went to attack a Castle with 134 Dragons, etc.... but I still get beaten... the troops, except for the flying ones, just stand at the castle walls and can't get through, and they are slowly being destroyed... I guess I'll have to restart... why do I have to accumulate such a large army, Golems... hmm... I've already explored everything... either I'm stupid, or something else is wrong.