Sentinel 
Artifact Creature — Shapeshifter
: Change this creature's base toughness to 1 plus the power of target creature blocking or blocked by this creature. (This effect lasts indefinitely.)
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyLEGALvintageLEGALcommanderLEGAL