I Am Duskmourn is a common Ongoing Scheme card from Duskmourn: House of Horror Commander (DSC), collector number 334. Current market price: $0.35, TCGplayer market prices via Scryfall.
(An ongoing scheme remains face up until it's abandoned.) At the beginning of your end step, you may cast a spell from your hand without paying its mana cost. If you do, abandon this scheme.