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.