Heroes 5.5 WarGame Edition - Tactical Edition.

Personally, I really don't like the "vampirism" spell, and not because of the "drain" ability it grants, but because it turns a unit into "undead" – in my opinion, this feels more like necromancy than dark magic.
P.S. Question: is the spell granted as a perk through a script, or by configuring this perk through the game files? (I looked for it, but didn't find such a setting, so the conclusion is: either I didn't look in the right place, or it needs to be done through a script).