(Palace Slagheap isn't a spell.)

When Palace Slagheap enters the battlefield, return a land you control to its owner's hand.

Palace Slagheap is indestructible. (Destroy effects and lethal damage don't destroy it.)

, Pay 1 life, Sacrifice Palace Slagheap: Search your library for a Swamp or Mountain card and put it onto the battlefield, then shuffle your library.