Mass Manipulation

• WWizards of the Coast2019-01-25
  Official Ruling
  In a multiplayer game, if a player leaves the game, all cards that player owns leave as well, and any effects that give the player control of permanents immediately end.
• WWizards of the Coast2019-01-25
  Official Ruling
  The control-change effect of Mass Manipulation lasts indefinitely. It doesn’t wear off during the cleanup step.

Rulings via Scryfall