(Forest Knoll isn't a spell.)
Forest Knoll enters the battlefield tapped.
, : Tap target artifact with converted mana cost X or less.
: Add or to your mana pool.
: Add to your mana pool. Put Forest Knoll on top of your library.
, 
: Tap target artifact with converted mana cost X or less.: Add 
or 
to your mana pool.: Add 
to your mana pool. Put Forest Knoll on top of your library.
