Oh Planar Chaos, you so crazy! This honestly makes a lot of sense to me. Vampires have always been black, so it only makes sense that something that drains life gains you life as well. I also like this card because it hasn't been errata'd to lifelink, meaning it stacks with cards like Blood Baron of Vizkopa and Voracious Hatchling. I still think my favourite combo with this card involves Sleeper Agent. Actually, that's not really a combo. It's just awesome. Still, it's an Aura, meaning some card disadvantage when the creature dies, but who cares? This card is still awesome.
Pros: Better-than-lifelink in black
Cons: Requires a creature