Dawnbreak Reclaimer — ruling 1

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.

Dawnbreak Reclaimer — ruling 2

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.

Dawnbreak Reclaimer : règles, fonctionnement et interactions (MTG)

Dawnbreak Reclaimer is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Flying At the beginning of your end step, choose a creature card in an opponent's graveyard, then that player chooses a creature card in your graveyard. You may return those cards to the battlefield under their owners' control.

How it works : Dawnbreak Reclaimer

Original English text — Wizards of the Coast / Scryfall

#1November 4, 2015· Wizards of the Coast
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.
No other card is named in this ruling.
#2November 4, 2015· Wizards of the Coast
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.
No other card is named in this ruling.