Hoyk's Horde

Hoyk's Horde enters the battlefield tapped with
X+1 +1/+1 counters on it.
Whenever another Centaur enters the battlefield,
put a +1/+1 counter on Hoyk's horde. Untap it.
{r/g}, remove a +1/+1 counter from Hoyk's Horde: Choose one —
- All Centaurs get +1/+1 until end of turn.
- Regenerate target Centaur.
- Hoard. (Treasure!)