Olvey, Evolved

Defender
Whenever you play a card with “evol” in its name, you may put a -1/-1 counter on Olvey.
If you do, create an artifact token called
Olvey’s Eye with “ 2 : Put a +1/+1 counter on target creature.”
Sacrifice four Olvey’s Eyes: you may cast a spell with “evol” in its name without paying its mana cost.