Impelled Giant | Magic: The Gathering
Formats Impelled Giant is Legal in
Official Oracle Text for Impelled Giant
Tap an untapped red creature you control other than Impelled Giant: Impelled Giant gets +X/+0 until end of turn, where X is the power of the creature tapped this way.
Official Rulings for Impelled Giant
8/1/2008 : The power of the creature you tap is checked as the ability resolves, not as the creature is tapped, and not at any later time should the power of that creature change. If that creature is no longer on the battlefield as the ability resolves, use the power it had when it was last on the battlefield.