Is Mournwhelk legal in Standard, Modern, and Commander?

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

What type of card is Mournwhelk?

Mournwhelk is a Creature — Elemental. Its oracle text reads: "When this creature enters, target player discards two cards. Evoke {3}{B} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.) *It hoards Lorwyn's rare sorrows.* Power/Toughness: 3/3"