Old Man Willow 
Legendary Creature — Treefolk
Old Man Willow's power and toughness are each equal to the number of lands you control. Whenever Old Man Willow attacks, you may sacrifice another creature or a token. When you do, target creature an opponent controls gets -2/-2 until end of turn.
Legality
standardNOT LEGALpioneerNOT LEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL