Bloodstone (3.5e Equipment)
From D&D Wiki
Bloodstone: Nasty little items that look like blood red, perfect rubies, Bloodstones are a curse wherever they are found. Whenever a living creature picks one up the stone sucks blood from them in a manner similar to the Vampiric Touch Spell causing 2d6 points of damage. Individuals killed by one of these stones arise as a Vampire Spawn. The stones store this blood energy and can be used by creatures that feed on blood as an alternate food source, every five points of blood stored in the stone acts as a 'successful drain' per the creatures blood feed ability.