…it involved bellyrubs
The Doclopedia #2,591
A Few New Monsters: Mana Vampire
These highly specialized vampires subsist on the mana, or magical energy, of humanoids who use or cast spells. Losing mana won’t kill anyone, but spellcasters who lose enough of it may not be able to cast spells for weeks.
Mana vampires are undead, but do not have fangs. Instead they have eyes that are somewhat larger than normal, and it the gaze from these eyes that stuns the victim and steals the mana.
Mana vampires have all of the usual vampire strengths and weaknesses, except that they are not vulnerable to holy water and they cannot ever cast spells or use magic items.