(Graven Cavern isn't a spell.)
Graven Cavern enters the battlefield tapped unless you pay 2 life.
, : Look at target player's hand.
: Add or to your mana pool.
Put Graven Cavern on top of your library: Add to your mana pool.
, 
: Look at target player's hand.: Add 
or 
to your mana pool. to your mana pool. 
