Hoarder of Heartbeats

Flying
Whenever another creature enters the battlefield, put a -1/-1 counter on it and a +1/+1 counter on Hoarder of Heartbeats.
When Hoarder of Heartbeats dies, creatures you control get +X/+0 until end of turn, where X is its power.
"Patience is a virtue, but wrath is not a sin."