Mournwhelk
Creature — Elemental
When this creature enters, target player discards two cards.
Evoke 
(You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)
It hoards Lorwyn's rare sorrows.
Jeremy Jarvis
Lorwyn (LRW)
• #127Rulings
If 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.
(wotc • 2013-04-15)
Rulings
If 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.
(wotc • 2013-04-15)