Kren, Dragonlord of Keeping

Flying, Double Strike
When a land enters the battlefield under an opponent's control, they may pay {2}. If they don't, search your library for a basic land and put it onto the battlefield tapped. When an opponent draws a card, they may pay {2}, if they don't, draw a card.
At each end step, if Kren is in exile or in a graveyard, return it to the battlefield