Is Merfolk of the Depths legal in Standard, Modern, and Commander?

Merfolk of the Depths is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Pauper.

Merfolk of the Depths

Q: What type of card is Merfolk of the Depths?

Merfolk of the Depths is a Creature — Merfolk Soldier. Its oracle text reads: "Flash (You may cast this spell any time you could cast an instant.) *When giant sinkholes opened across Ravnica, they revealed buried oceans and the merfolk, once thought to be extinct.* Power/Toughness: 4/2"