Cavern of Souls is a mythic Land card from Double Masters 2022 (2X2), collector number 320. Current market price: $47.82 (foil $54.72), TCGplayer market prices via Scryfall.
As this land enters, choose a creature type. {T}: Add {C}. {T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.