I can boast that I managed to defeat opponents even with anti-magic and without phoenix messengers. The key is to eliminate the stack of Knights as quickly as possible. Even if they destroy 1-2 stacks, it's not a big deal. The main thing is to properly develop the Necromancer, so that luck is on your side. I especially want to note that in the early stages, leadership is a key factor for the success of the Necropolis faction; it might even be enough to defeat the Knights. And after the Knight stack is eliminated, it usually doesn't take much effort to finish off the remaining enemy units.

It should also be noted that it is desirable to keep the Vampires. With blindness, they can easily deal with the Knights.