Groundhunter Vanguard

Whenever, Groundhunter Vanguard deals combat damage to a player, create a 3/3 green Bird creature token with "{2}, Sacrifice a
creature: Put a +1/+1 counter on this creature."
"The existence of the vanguard is undeniable proof of the Terror Birds' intelligence. It also explains how they always know to find the best hunting grounds.
—Gledon, Megafauna Biologist