Twisted Riddlekeeper is a uncommon Creature — Eldrazi Sphinx card from Modern Horizons 3 (MH3), collector number 14. Current market price: $0.14 (foil $0.30), TCGplayer market prices via Scryfall.
Emerge {5}{C}{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 two target permanents. Put a stun counter on each of them. (If a permanent with a stun counter would become untapped, remove one from it instead.) Flying