Elder Deep-Fiend is a rare Creature — Eldrazi Octopus card from Eldritch Moon (EMN), collector number 5. Current market price: $0.28 (foil $0.28), TCGplayer market prices via Scryfall.
Flash Emerge {5}{U}{U} (You may cast this spell by sacrificing a creature and paying the emerge cost reduced by that creature's mana value.) When you cast this spell, tap up to four target permanents.