Problems with Heroes of Might and Magic IV.

and in 4 I used to create a phantom or illusion (I don't remember now) of a vampire. it hits and drains life, and it has no unit cap. as a result, even when the enemy has a huge advantage at the start, by the end of the battle there are so many vampires that even the strongest army falls:)

by the way, you could summon vampires first and then make an illusion from them:)

And it's really "fun" when your entire stack gets dispelled.
And in 4, there is a counter for everyone; for example, for the Great and Powerful Vampires, there's a simple answer—either the Death Ward spell or a relatively similar-sized group of Swordsmen (or Crusaders, whatever they were called). For a vampire, Black Dragons are even scarier.:)