Bullockornis

{3}{w}{w}{w}: Monstrosity 3 (If this creature isn’t monstrous, put 3 +1/+1 counters on it and it becomes monstrous.)
When Bullockornis becomes monstrous, creatures without flying your opponents control can't block this turn.
Bullockornis planei, nicknamed the Demon-Duck of Doom or Thunderbird, is an extinct flightless bird that lived in what is now Australia.