Constant Mists is a uncommon Instant card from Stronghold (STH), collector number 104. Current market price: $19.20, TCGplayer market prices via Scryfall.
Buyback—Sacrifice a land. (You may sacrifice a land in addition to any other costs as you cast this spell. If you do, put this card into your hand as it resolves.) Prevent all combat damage that would be dealt this turn.