(: Add or to your mana pool.)
When Hollow Karoo enters the battlefield, you lose 2 life unless you reveal an artifact card from your hand.
, Sacrifice a Swamp: Add to your mana pool.
, : You gain 1 life.
: Add 
or 
to your mana pool.), Sacrifice a Swamp: Add to your mana pool.
, : You gain 1 life.
