Would you like to play as a Necromancer with the ability to upgrade Vampires?

Why don't you try it? Preferably not with a level 1 hero, but with someone reasonably leveled up. Vampires and 6 units, put them in the first stack, for example. First, use Time Stop, and then position yourself in a corner of the map. Two stacks of griffons will fly over and attack them. You'll come out of there with losses of 6 units and 4 angels.