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.
You don't choose a target for Old Man Willow's last ability at the time it triggers. Rather, a second "reflexive" ability triggers when you sacrifice a creature or token this way. You choose a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.