Historical Rules · 30 September 2016
Rule 901.10
Official source text from the 30 September 2016 Rules release
When a player leaves the game, all objects owned by that player except abilities from phenomena leave the game. (See rule 800.4a.) If that includes a face-up plane card or phenomenon card, the planar controller turns the top card of his or her planar deck face up. This is not a state-based action. It happens as soon as the player leaves the game.