Karn, Silver Golem is a rare Legendary Artifact Creature — Golem card from Commander's Arsenal Oversized (OCM1), collector number 6. Current market price: — (foil $10.82), TCGplayer market prices via Scryfall.
Whenever Karn blocks or becomes blocked, it gets -4/+4 until end of turn. {1}: Target noncreature artifact becomes an artifact creature with power and toughness each equal to its mana value until end of turn.