Giant Boa

Giant Boa enters the battlefield tapped. It doesn't
untap during your untap step for as long as it has
a digest counter on it.
{1}{b}{b}, {t}: Giant Boa fights target creature you
don't control. Then and whenever a creature that
fights Giant Boa would be put into its owner's
graveyard, exile it instead. Put a +1/+1 counter
and X digest counters on Giant Boa, where X is
the exiled creature's toughness. At the beginning
of each upkeep, remove a digest counter from
Giant Boa.