Gruul Keyrune
Artifact
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or 
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: This artifact becomes a 3/2 red and green Beast artifact creature with trample until end of turn.
As perilous and unpredictable as the wilds themselves.
Daniel Ljunggren
Gatecrash (GTC)
• #230Rulings
Activating the ability that turns the Keyrune into a creature while it's already a creature will override any effects that set its power and/or toughness to another number, but effects that modify power and/or toughness without directly setting them will still apply.
(wotc • 2013-04-15)
Until the ability that turns the Keyrune into a creature resolves, the Keyrune is colorless.
(wotc • 2013-04-15)
Rulings
Activating the ability that turns the Keyrune into a creature while it's already a creature will override any effects that set its power and/or toughness to another number, but effects that modify power and/or toughness without directly setting them will still apply.
(wotc • 2013-04-15)
Until the ability that turns the Keyrune into a creature resolves, the Keyrune is colorless.
(wotc • 2013-04-15)