Slumbering Cerberus 

Creature — Dog
This creature doesn't untap during your untap step. Morbid — At the beginning of each end step, if a creature died this turn, untap this creature.
Legality
standardLEGALpioneerLEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL