(Obsidian Weald isn't a spell.)

Obsidian Weald enters the battlefield tapped unless you sacrifice a creature.

Obsidian Weald is indestructible. (Destroy effects and lethal damage don't destroy it.)

, Pay 1 life, Sacrifice Obsidian Weald: Search your library for a Swamp or Forest card and put it onto the battlefield, then shuffle your library.