Slavarg, The Undying

You can only have one copy of Slavarg, The
Undying in your library.
At the beginning of your upkeep, return Slavarg
from your graveyard or exile to the battlefield.
Slavarg enters the battlefield with a +1/+1
counter on it for each time it left the graveyard
or exile during this game, then you may have it
fight target creature.