Mm'menon, the Right Hand is a rare Legendary Creature — Jellyfish Advisor card from Edge of Eternities Promos (PEOE), collector number 68p. Current market price: $0.43 (foil $0.63), TCGplayer market prices via Scryfall.
Flying You may look at the top card of your library any time. You may cast artifact spells from the top of your library. Artifacts you control have "{T}: Add {U}. Spend this mana only to cast a spell from anywhere other than your hand."