Bouldergeist

At the beginning of your upkeep you may
remove any number of rage counters from
Bouldergeist, if you do deal X damage to target
player, where X is the amount of rage counters
removed this way from Bouldergeist. At the
beginning of each end step, put a rage counter
on Bouldergeist for each creature an opponent
controls that attacked you or a planeswalker
you control.
"Watch out for those Boulders!!"