Eventide

Noxious Hatchling

Noxious Hatchling comes into play with four -1/-1 counters on it.
Wither (This deals damage to creatures in the form of -1/-1 counters.)
Whenever you play a black spell, remove a -1/-1 counter from Noxious Hatchling.
Whenever you play a green spell, remove a -1/-1 counter from Noxious Hatchling.

Noxious Hatchling enters with four -1/-1 counters on it.
Wither (This deals damage to creatures in the form of -1/-1 counters.)
Whenever you cast a black spell, remove a -1/-1 counter from Noxious Hatchling.
Whenever you cast a green spell, remove a -1/-1 counter from Noxious Hatchling.