(River Clachan isn't a spell.)
When River Clachan enters the battlefield, sacrifice it unless you pay 2 life.
: Target player exiles a card from his or her graveyard.
: Add or to your mana pool.
Sacrifice River Clachan: Add or to your mana pool.
: Target player exiles a card from his or her graveyard.: Add 
or 
to your mana pool. or to your mana pool.
