Hissing Quagmire is a rare Land card from Oath of the Gatewatch Promos (POGW), collector number 171s. Current market price: — (foil $2.99), TCGplayer market prices via Scryfall.
This land enters tapped. {T}: Add {B} or {G}. {1}{B}{G}: Until end of turn, this land becomes a 2/2 black and green Elemental creature with deathtouch. It's still a land.