Is Gravelgill Duo legal in Standard, Modern, and Commander?

Gravelgill Duo is legal in: Modern, Legacy, Vintage, Commander, Pauper.

Gravelgill Duo

Q: What type of card is Gravelgill Duo?

Gravelgill Duo is a Creature — Merfolk Rogue Warrior. Its oracle text reads: "Whenever you cast a blue spell, this creature gets +1/+1 until end of turn. Whenever you cast a black spell, this creature gains fear until end of turn. (It can't be blocked except by artifact creatures and/or black creatures.)"

Creature — Merfolk Rogue Warrior

Whenever you cast a blue spell, this creature gets +1/+1 until end of turn.

Whenever you cast a black spell, this creature gains fear until end of turn. (It can't be blocked except by artifact creatures and/or black creatures.)

Set Shadowmoor

Rarity Common

Mana Value 3

Artist Brandon Kitkouski

Collector # 165

Scryfall Gatherer