Dr. House, Diagnostic Genius

When a creature enters the battlefield under
your control, create a Pill token. (It's an artifact
with "{1}, Sacrifice this artifact: Target creature gains protection from color of choice until end of turn, that creature gets a -1/-1 counter on the next end step.")
At the beginning of each end step, If you
sacrificed three or more Pill tokens this turn,
return target creature that died this turn from
your graveyard to the battlefield.