Iwamori of the Open Fist

• WWizards of the Coast2018-03-16
  Official Ruling
  When Iwamori's triggered ability resolves, first the player whose turn it is (if that player is an opponent) may choose a legendary creature card in hand without revealing it, then each other opponent in turn order may do the same, then all chosen cards are put onto the battlefield at the same time.

Rulings via Scryfall