Can you suggest how to lure the Necromancers out of the castle? Maybe someone has an idea. I even ran around with secondary heroes to lure them out, but there are 200 liches inside, and I started the mission with a Warrior and chose the Path of Blood. There's no summoning ability, although accumulating 1000 points by the 2nd mission also seems a bit harsh. By the time I break down the gates, he's already taken out 40 dogs with just liches. It's possible to win, but it's a pity for the dogs, and there's nothing to resurrect them with. It's generally difficult against Necromancers; draining doesn't work, there are no flying units for the Demon, teleportation is only available for the Demon Mage, and it's also difficult to reach level 15 by the 2nd mission.
You can weaken enemies in castles using the standard method; usually, they deploy a secondary hero at the castle gates, giving him about 10% of the army. You can repeatedly defeat this secondary hero with minimal losses, or even without any losses, without attacking the main hero. Gradually, the main hero's army will decrease.