Karn, Silver Golem

Legendary Artifact Creature - Golem 4/4, 5 (5)
Whenever Karn, Silver Golem 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 converted mana cost until end of turn. (That artifact retains its abilities.)¹
Illus. Mark Zug

Gatherer Card Rulings [Nov 2009]

• 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 is subject to the "summoning sickness" rule: It can only attack, and its {T} abilities can only be activated, if its controller has continuously controlled that permanent since the beginning of his or her most recent turn.

Format Legality	Legal in Vintage, Legacy Banned in Extended, Standard
Printings (2/7)	Arena League prize (1999) (Special) Urza's Saga (Rare)