Karn, the Great Creator is a rare Legendary Planeswalker — Karn card from War of the Spark Promos (PWAR), collector number 1p. Current market price: $4.67 (foil $7.07), TCGplayer market prices via Scryfall.
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.