Vecna, Curse-Bearer

Vecna's Curse - At your endstep, choose an
opponent. Until your next turn, you may exile
the top card of their library and cast spells from
among those exiled this way by paying life instead
of its mana cost. Put a curse counter on Vecna,
Curse-Bearer.
{b}{b}{b}, {t}: If you've lost life this turn, remove 3
curse counters from Vecna, Curse-Bearer, and
add {u}{b}{r}. Use this mana only to cast cards
from exile.