Is Chillerpillar legal in Standard, Modern, and Commander?

Chillerpillar is legal in: Modern, Legacy, Vintage, Commander, Pauper.

Chillerpillar

Q: What type of card is Chillerpillar?

Chillerpillar is a Snow Creature — Insect. Its oracle text reads: "{4}{S}{S}: Monstrosity 2. (If this creature isn't monstrous, put two +1/+1 counters on it and it becomes monstrous. {S} can be paid with one mana from a snow source.) As long as this creature is monstrous, it has flying."

Snow Creature — Insect

: Monstrosity 2. (If this creature isn't monstrous, put two +1/+1 counters on it and it becomes monstrous. can be paid with one mana from a snow source.)