(Slagheap Tar Pit isn't a spell.)

At the beginning of your end step, if you didn't cast any spells this turn, Slagheap Tar Pit deals 1 damage to you.

, : Tap target artifact with converted mana cost X or less.

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