Tezzeret's Gatebreaker

Tezzeret's Gatebreaker

Artifact (CMC 4)
When Tezzeret's Gatebreaker enters the battlefield, look at the top five cards of your library. You may reveal a blue or artifact card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.
, , Sacrifice Tezzeret's Gatebreaker: Creatures you control can't be blocked this turn.