(Salt Grave isn't a spell.)
At the beginning of your end step, if you didn't cast any spells this turn, Salt Grave deals 1 damage to you.
Salt Grave is indestructible. (Destroy effects and lethal damage don't destroy it.)
, Pay 1 life, Sacrifice Salt Grave: Search your library for a Plains or Swamp card and put it onto the battlefield, then shuffle your library.