Vouchsafe

Prevent all combat damage that would be dealt
to target player this turn, then you may exile Vouchsafe with up to that many debt counters
on it.
While Vouchsafe is exiled, you may pay {x}{b}{b}, where X is the number of debt counters
on it. If you do, remove all debt counters from it
and the player it targeted loses X life and you
gain X life.