When Khalni Gem enters the battlefield, return two lands you control to their owner's hand. : Add two mana of any one color to your mana pool.
A fragment of ancient power lost in the heart of Ora Ondar.
Official Rulings for Khalni Gem
10/1/2009 : If you don't control any lands by the time Khalni Gem's triggered ability resolves, nothing happens. If you control just one, you'll have to return it to its owner's hand. Khalni Gem isn't affected in either case.