Case of the Locked Hothouse is a rare Enchantment — Case card from Murders at Karlov Manor (MKM), collector number 155. Current market price: $3.55 (foil $3.82), TCGplayer market prices via Scryfall.
You may play an additional land on each of your turns. To solve — You control seven or more lands. (If unsolved, solve at the beginning of your end step.) Solved — You may look at the top card of your library any time, and you may play lands and cast creature and enchantment spells from the top of your library.