Steam Vents is a rare Land — Island Mountain card from Guilds of Ravnica Promos (PGRN), collector number 257p. Current market price: $13.18 (foil $10.26), TCGplayer market prices via Scryfall.
({T}: Add {U} or {R}.) As this land enters, you may pay 2 life. If you don't, it enters tapped.