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 artifact: Draw a card.") {B}, {T}, Pay 1 life: Create a 1/1 white and black Vampire creature token with lifelink. {B}{B}, {T}, Sacrifice Glass-Cast Heart and thirteen Blood tokens: Each opponent loses 13 life and you gain 13 life.