Unexpected Potential

Hidden agenda (Start the game with this conspiracy face down in the command zone and secretly choose a card name. You may turn this conspiracy face up any time and reveal that name.) You may spend mana as though it were mana of any color to cast spells with the chosen name.

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6ofws6beejpb1h4w5f1eho.