Karn, Silver Golem
Legendary Artifact Creature (CMC:5)
Whenever Karn, Silver Golem blocks or becomes blocked, it gets -4/+4 until end of turn. : Target noncreature artifact becomes an artifact creature with power and toughness each equal to its converted mana cost until end of turn.
6 V10 • ENMark Zug
™ & © 1993—2010 Wizards of the Coast
Legal in: Urza Block,Legacy,Vintage,Freeform,Prismatic,Tribal Wars Legacy,Singleton 100,Commander
Oracle Text (click to copy):
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10/4/2004 The blocking ability triggers only once no matter how many blockers are declared. 8/1/2008 A noncreature permanent that turns into a creature can attack, and its abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of his or her most recent turn. It doesn't matter how long the permanent has been a creature.