(Swamp Hollows isn't a spell.)
Swamp Hollows enters the battlefield tapped unless you sacrifice a planeswalker.
, : Look at target player's hand.
: Add or to your mana pool.
Sacrifice Swamp Hollows: Add or to your mana pool.
, 
: Look at target player's hand.: Add 
or 
to your mana pool. or to your mana pool.
