Heart of Monsters

At each upkeep, create a 2/2 green Hydra
creature token with "When this creature dies,
put a blood counter on Heart of Monsters"
When Heart of Monsters has 10 or more Blood
counters on it, permanents you control gain
+3/+3 and "{b}{g}{2}{t}: Destroy target creature".
The Heart of Monsters is the only place known
where even the Dragons won't roam.