Null Summoner is a rare Creature — Human Warlock card from Reality Fracture (FRA), collector number 142. Current market price: $0.18 (foil $0.31), TCGplayer market prices via Scryfall.
When this creature enters, if you cast it, target opponent reveals their hand. You choose a nonland card from it. Exile that card. Threshold — As long as there are seven or more cards in your graveyard, you may cast the exiled card, and mana of any type can be spent to cast that spell.