(Sea Knoll isn't a spell.)
When Sea Knoll enters the battlefield, sacrifice it unless you pay .
Sacrifice a land: You gain 1 life.
: Add or to your mana pool.
: Add to your mana pool. Put Sea Knoll on top of your library.
.
: Add or 
to your mana pool.: Add 
to your mana pool. Put Sea Knoll on top of your library.
