Aerie Ouphes — ruling 1

If a creature with persist that has +1/+1 counters on it receives enough -1/-1 counters to cause it to be destroyed by lethal damage or put into its owner’s graveyard for having 0 or less toughness, persist won’t trigger and the card won’t return to the battlefield. That’s because persist checks the creature’s existence just before it leaves the battlefield, and it still has all those counters on it at that point.

Aerie Ouphes — ruling 2

If a creature with persist stops being a creature, persist will still work.

Aerie Ouphes — ruling 3

The persist ability triggers when the permanent is put into a graveyard. Its last known information (that is, how the creature last existed on the battlefield) is used to determine whether it had a -1/-1 counter on it.

Aerie Ouphes — ruling 4

If a permanent has multiple instances of persist, they’ll each trigger separately, but the redundant instances will have no effect. If one instance returns the card to the battlefield, the next to resolve will do nothing.

Aerie Ouphes — ruling 5

If a token with no -1/-1 counters on it has persist, the ability will trigger when the token is put into the graveyard. However, the token will cease to exist and can’t return to the battlefield.

Aerie Ouphes — ruling 6

When a permanent with persist returns to the battlefield, it’s a new object with no memory of or connection to its previous existence.

Aerie Ouphes — ruling 7

If multiple creatures with persist are put into the graveyard at the same time (due to combat damage or a spell that destroys all creatures, for example), the active player (the player whose turn it is) puts all of their persist triggers on the stack in any order, then each other player in turn order does the same. The last trigger put on the stack is the first one that resolves. That means that in a two-player game, the nonactive player’s persist creatures will return to the battlefield first, then the active player’s persist creatures do the same. The creatures return to the battlefield one at a time.

Aerie Ouphes — ruling 8

If Aerie Ouphes has no -1/-1 counters on it when you sacrifice it to activate its first ability, persist will return Aerie Ouphes to the battlefield with a -1/-1 counter on it before that ability resolves. The ability will check the power of Aerie Ouphes at the time you sacrificed it, not the power of the returned Aerie Ouphes (which is actually a new object with no relation to its previous existence).

Aerie Ouphes : règles, fonctionnement et interactions (MTG)

Aerie Ouphes 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

Sacrifice this creature: It deals damage equal to its power to target creature with flying. Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

How it works : Aerie Ouphes

Original English text — Wizards of the Coast / Scryfall

#1June 7, 2013· Wizards of the Coast
If a creature with persist that has +1/+1 counters on it receives enough -1/-1 counters to cause it to be destroyed by lethal damage or put into its owner’s graveyard for having 0 or less toughness, persist won’t trigger and the card won’t return to the battlefield. That’s because persist checks the creature’s existence just before it leaves the battlefield, and it still has all those counters on it at that point.
No other card is named in this ruling.
#2June 7, 2013· Wizards of the Coast
If a creature with persist stops being a creature, persist will still work.
No other card is named in this ruling.
#3June 7, 2013· Wizards of the Coast
The persist ability triggers when the permanent is put into a graveyard. Its last known information (that is, how the creature last existed on the battlefield) is used to determine whether it had a -1/-1 counter on it.
No other card is named in this ruling.
#4June 7, 2013· Wizards of the Coast
If a permanent has multiple instances of persist, they’ll each trigger separately, but the redundant instances will have no effect. If one instance returns the card to the battlefield, the next to resolve will do nothing.
No other card is named in this ruling.
#5June 7, 2013· Wizards of the Coast
If a token with no -1/-1 counters on it has persist, the ability will trigger when the token is put into the graveyard. However, the token will cease to exist and can’t return to the battlefield.
No other card is named in this ruling.
#6June 7, 2013· Wizards of the Coast
When a permanent with persist returns to the battlefield, it’s a new object with no memory of or connection to its previous existence.
No other card is named in this ruling.
#7June 7, 2013· Wizards of the Coast
If multiple creatures with persist are put into the graveyard at the same time (due to combat damage or a spell that destroys all creatures, for example), the active player (the player whose turn it is) puts all of their persist triggers on the stack in any order, then each other player in turn order does the same. The last trigger put on the stack is the first one that resolves. That means that in a two-player game, the nonactive player’s persist creatures will return to the battlefield first, then the active player’s persist creatures do the same. The creatures return to the battlefield one at a time.
No other card is named in this ruling.
#8August 1, 2008· Wizards of the Coast
If Aerie Ouphes has no -1/-1 counters on it when you sacrifice it to activate its first ability, persist will return Aerie Ouphes to the battlefield with a -1/-1 counter on it before that ability resolves. The ability will check the power of Aerie Ouphes at the time you sacrificed it, not the power of the returned Aerie Ouphes (which is actually a new object with no relation to its previous existence).
No other card is named in this ruling.