(Krosan of the Burnwillows isn't a spell.)
When Krosan of the Burnwillows enters the battlefield, you lose 2 life unless you reveal an Orc card from your hand.
, : Tap target artifact with converted mana cost X or less.
: Add or to your mana pool.
, 
: Tap target artifact with converted mana cost X or less.: Add 
or 
to your mana pool.
