Graven Den enters the battlefield tapped unless you sacrifice an artifact.
: Add or to your mana pool.
Put Graven Den on top of your library: Add to your mana pool.
, Sacrifice Graven Den: Add to your mana pool.
: Add 
or 
to your mana pool.
to your mana pool. , Sacrifice Graven Den: Add 
to your mana pool.
