2015-11-04 : If any opponent has a creature card in their graveyard as Dawnbreak Reclaimer’s ability resolves, then you must choose one of those cards. You can’t choose a different opponent with no creature cards in their graveyard to avoid returning one of those cards.

2015-11-04 : If there are no creature cards in any opponent’s graveyard as Dawnbreak Reclaimer’s ability resolves, you’ll still have the option to return a creature card from your graveyard to the battlefield. You choose which opponent will choose a creature card in your graveyard.