Heartless Conscription is a rare Sorcery card from Outlaws of Thunder Junction Commander (OTC), collector number 21. Current market price: $2.41, TCGplayer market prices via Scryfall.
Exile all creatures. For each card exiled this way, you may play that card for as long as it remains exiled, and mana of any type can be spent to cast that spell. Exile Heartless Conscription.