As long as Guardian Graveyard is not a creature, it has indestructible.

{t}: Add {c}.

{1}, {t}: Add one mana of any color.

{3}: Guardian Graveyard becomes a 2/2 Construct creature until end of turn. If three or more colors were used to pay for this cost, it becomes a 4/4 Construct creature until end of turn instead. It’s still an artifact land.