(Forbidding Grave isn't a spell.)
Forbidding Grave enters the battlefield tapped.
Sacrifice a land: You gain 1 life.
: Add or to your mana pool.
: Add to your mana pool. Put Forbidding Grave on top of your library.
: Add 
or 
to your mana pool.: Add 
to your mana pool. Put Forbidding Grave on top of your library.
