Hissing Quagmire is a rare Land card from Edge of Eternities: Stellar Sights (EOS), collector number 19. Current market price: $0.53 (foil $0.64), 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.