Karn, the Great Creator - Bloomburrow Commander

Activated abilities of artifacts your opponents control can't be activated.

[+1]: Until your next turn, up to one target noncreature artifact becomes an artifact creature with power and toughness each equal to its mana value.

[−2]: You may reveal an artifact card you own from outside the game or choose a face-up artifact card you own in exile. Put that card into your hand.