Light or Dark magic.

even if the hero doesn't have much magic power, a stable 50% creature will draw +2% for each spell power, which in any case, guarantees more than vampires.

The problem is that when playing against dwarves, you shouldn't use this spell because they have a rune (I don't remember the name) that steals one of the enemy's positive effects. Now imagine berserkers with vampirism, when the madness rune (2 attacks instead of 1) is also applied to them, and the berserker ability is activated.