Glass-Cast Heart

Whenever one or more Vampires you control attack, create a Blood token. (It's an artifact with "1, T, Discard a card, Sacrifice this token: Draw a card.")

B, T, Pay 1 life: Create a 1/1 white and black Vampire creature token with lifelink.

BB, T, Sacrifice this artifact and thirteen Blood tokens: Each opponent loses 13 life and you gain 13 life.