Mournwhelk is a common Creature — Elemental card from Lorwyn (LRW), collector number 127. Current market price: $0.33 (foil $0.94), TCGplayer market prices via Scryfall.
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.)