Cavern of Corpses

At the beginning of your upkeep, roll a six-sided
die. Create a 0/X colorless Corpse creature token
with defender, where X is the result.
Whenever a corpse leaves the battlefield, put a
heap counter on Cavern of Corpses. Then, if
there are 4 or more heap counters on Cavern of Corpses, exile it and each opponent draws two
cards.