Tactics against Necromancers.

When playing against the AI, you can easily defeat any faction with any castle. But against a human player, if your opponent is a Necromancer, you need to act more thoughtfully. Don't rush in (they will be prepared and may even strike first, taking advantage of their numerical superiority). You need to prevent the Necromancer from creating cheap skeletons. Prepare magic, preferably slowing spells. At the beginning of the game, build up your powerful units as quickly as possible, but don't forget to save money to buy them.