Rienne, Angel of Rebirth

• WWizards of the Coast2019-07-12
  Official Ruling
  If Rienne dies at the same time as one or more other multicolored creatures you control, its last ability triggers for each of those creatures.
• WWizards of the Coast2019-07-12
  Official Ruling
  If an effect causes a non-multicolored creature to become multicolored and that creature dies, the non-multicolored card will return to its owner's hand.
• WWizards of the Coast2019-07-12
  Official Ruling
  If a multicolored creature you control leaves the graveyard after it dies but before the delayed triggered ability resolves, it will not return to its owner's hand.
• WWizards of the Coast2019-07-12
  Official Ruling
  If Rienne leaves the battlefield after its ability has triggered but before the next end step, its delayed triggered ability will still return the card.

Rulings via Scryfall