Lair of the Hydra
Magic: The Gatheringrare· Adventures in the Forgotten Realms Promos

Lair of the Hydra

If you control two or more other lands, this land enters tapped. {T}: Add {G}. {X}{G}: Until end of turn, this land becomes an X/X green Hydra creature. It's still a land. X can't be 0.