A new race: Vampires.

Seriously? What about the black riders??? Run around the map and you'll find such riders with black-purple swords on horses in red armor

The riders are a different matter. They didn't separate of their own free will. They are exiles from the world of necromancers. But vampires are the strike force of the Necropolis. Who would be left in its army without them? Just walking corpses and skeletons of all kinds. Vampires and necros are one and the same. And there is no need to try and divide them. After all, even some heroes of the Necropolis are vampires by biography. What would happen to someone like Kolya then? Rewrite the entire plot? No, undoubtedly, he could be made into a lich, but that's stupid. Vampires have always been creatures of necromancers; a separate vampire race is no longer Heroes of Might and Magic.

I certainly liked the description of the race, but it's not what's needed in HMM, imho.