Solas, The Dreadwolf

Whenever a permanent an opponent controls is put into a graveyard from the battlefield, put a +1/+1 counter on Solas, The Dreadwolf.

At the beginning of your upkeep, if Solas has one or more +1/+1 counters on it, you may remove all of them. If you do, exile each other nonland permanent with mana value less than or equal to the number of counters removed this way.