Purgatory — ruling 1

If this card changes controllers between putting the upkeep triggered ability on the stack and resolving it, the creature is put onto the battlefield under the control of the player who controlled this card when the ability was put on the stack.

Purgatory — ruling 2

This has been restored to a triggered ability that triggers when a nontoken creature is put into a graveyard from the battlefield, rather than a replacement effect. The creature does go to the graveyard, and will trigger any other abilities that look for this event.

Purgatory — ruling 3

If an opponent takes control of this card and pays for the upkeep ability, the creatures will enter under their control even if you exiled them.

Purgatory — ruling 4

If destroyed at the same time some creatures are destroyed, the destroyed creatures are exiled and stay exiled.

Purgatory : règles, fonctionnement et interactions (MTG)

Purgatory is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Whenever a nontoken creature is put into your graveyard from the battlefield, exile that card. At the beginning of your upkeep, you may pay and 2 life. If you do, return a card exiled with this enchantment to the battlefield.

How it works : Purgatory

Original English text — Wizards of the Coast / Scryfall

#1August 1, 2008· Wizards of the Coast
If this card changes controllers between putting the upkeep triggered ability on the stack and resolving it, the creature is put onto the battlefield under the control of the player who controlled this card when the ability was put on the stack.
No other card is named in this ruling.
#2April 1, 2008· Wizards of the Coast
This has been restored to a triggered ability that triggers when a nontoken creature is put into a graveyard from the battlefield, rather than a replacement effect. The creature does go to the graveyard, and will trigger any other abilities that look for this event.
No other card is named in this ruling.
#3October 4, 2004· Wizards of the Coast
If an opponent takes control of this card and pays for the upkeep ability, the creatures will enter under their control even if you exiled them.
No other card is named in this ruling.
#4October 4, 2004· Wizards of the Coast
If destroyed at the same time some creatures are destroyed, the destroyed creatures are exiled and stay exiled.
No other card is named in this ruling.