Chromium, the Mutable 
Legendary Creature — Elder Dragon
Flash This spell can't be countered. Flying Discard a card: Until end of turn, Chromium becomes a Human with base power and toughness 1/1, loses all abilities, and gains hexproof. It can't be blocked this turn.
Legality
standardNOT LEGALpioneerLEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL