Watchers of the Dead

• WWizards of the Coast2017-04-18
  Official Ruling
  An opponent with one or two cards in their graveyard won’t exile any cards.
• WWizards of the Coast2017-04-18
  Official Ruling
  When this ability resolves, first the player whose turn it is (if that player is an opponent) chooses two cards in their graveyard, then each other opponent in turn order does the same, then all of the other cards in their graveyards are exiled simultaneously. Each player will know the choices made by the players who chose before them.

Rulings via Scryfall