The Pit

The Pit enters the battlefield tapped.
{t} : Add {u}.
{2}{u}, {t} : Exile target creature until The Pit
leaves the battlefield. At the beginning of your
end step, if 5 or more creatures are exiled this
way, sacrifice The Pit.
Beware the depths of darkness that wait with chill embrace, for those doomed to dwell within the pit can
never leave that place.