Sunken Citadel is a rare Land — Cave card from The Lost Caverns of Ixalan Promos (PLCI), collector number 285s. Current market price: — (foil $1.58), TCGplayer market prices via Scryfall.
This land enters tapped. As it enters, choose a color. {T}: Add one mana of the chosen color. {T}: Add two mana of the chosen color. Spend this mana only to activate abilities of land sources.