Lurker in the Deep is a mythic Enchantment Creature — Fish Illusion card from Alchemy: Duskmourn (YDSK), collector number 6.
Impending 3—{2}{U}{U} Whenever Lurker in the Deep enters or attacks, seek a nonland card. Whenever you seek one or more cards during your turn, conjure a duplicate of each of those cards into your hand, then manifest those duplicates.