Cheapest priced copy (Lorwyn): $0.35 at Card Kingdom, near mint, their price list as of .
Mournwhelk 
Creature — Elemental · 3/3 · Common · Lorwyn · #127
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.)
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Lorwyn | 127 | Common | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 15 April 2013If you cast this card for its evoke cost, you may put the sacrifice trigger and the regular enters-the-battlefield trigger on the stack in either order. The one put on the stack last will resolve first.