Self Sacrifice

Unkown, Flying
Offering {3} (As you cast this creature you may pay {3}. If you do, put this creature into your graveyard.
Exile cards from the top of your graveyard until you
exile a card with unknown. Put that card onto the battlefield.)
Creature cards in your hand have Offering{3}.
If you don't pay this cards offering cost as you
cast it. It enters the battlefield with a +1/+1
counter.