The Animal, Ice Cave Rocker

Whenever a permanent an opponent controls is
put into a graveyard from the battlefield, put a
+1/+1 counter on The Animal, Ice Cave Rocker.
At the beginning of your upkeep, if the Animal,
Ice Cave Rocker has one or more +1/+1
counters on it, you may remove all of them.
If you do, exile each nonland permanent with
converted mana cost less than or equal to the
number of counters removed this way.