HoMM IV Reference Guide.

If there are vampires and other monsters in the army, then when one vampire is lost, you can cast Sacrifice on another unit – there will be more vampires than the initial number, but they will remain even after the battle. Thus, you can significantly increase the number of vampires by using random monsters.

Isn't that right?

Added 34 minutes later
Order magic is valuable primarily at higher levels. But it is difficult to level up two strong mages at once. The combination of Hypnosis + Sacrifice is a very powerful combination.

This is also incorrect.

For starters, I would advise you to read the "from the author" preamble at the very beginning of the manual. It contains explanations for many questions. Since I don't use Sacrifice myself, I had to rely on the word of the person who wrote it. Moreover, Hypnosis + Sacrifice did not contradict logic and worked during testing (although I checked it a long time ago, I don't remember the details). For example, a Martyr with Hypnosis works great, but... only for 3 turns, after which everything needs to be repeated.
Regarding vampires. The Raise Dead spell should not be cast on vampires. The AI counts the total number of vampires and limits their self-healing, and after the battle, the revived creatures disappear. I assume that Sacrifice has a similar mechanism, and there will definitely be no resurrection by necromancy after the battle.
I can add that by the time the hero reaches level 5 magic, it is pointless to carry meat around specifically for Sacrifice, and sacrificing a combat slot is not advisable.
However, I will test this spell when I have time.:smile24: :smile31: