Pegasus Guardian // Rescue the Foal — ruling 1

Pegasus Guardian's triggered ability will trigger even if Pegasus Guardian wasn't under your control at the time the permanent you controlled left the battlefield.

Pegasus Guardian // Rescue the Foal — ruling 2

When the card exiled by Rescue the Foal returns to the battlefield, it will be a new object with no connection to the card that was exiled. Auras attached to the exiled creature will be put into their owners' graveyards. Any Equipment will become unattached and remain on the battlefield. Any counters on the exiled creature will cease to exist.

Pegasus Guardian // Rescue the Foal — ruling 3

If a token is exiled this way, it will cease to exist and won't return to the battlefield.

Pegasus Guardian // Rescue the Foal — ruling 4

An adventurer card is a permanent card in every zone except the stack, as well as while on the stack if not cast as an Adventure. Ignore its alternative characteristics in those cases. For example, while it’s in your graveyard, Altar of Bhaal is an artifact card whose mana value is 2.

Pegasus Guardian // Rescue the Foal — ruling 5

When casting a spell as an Adventure, use the alternative characteristics and ignore all of the card’s normal characteristics. The spell’s color, mana cost, mana value, and so on are determined by only those alternative characteristics. If the spell leaves the stack, it immediately resumes using its normal characteristics.

Pegasus Guardian // Rescue the Foal — ruling 6

If you cast an adventurer card as an Adventure, use only its alternative characteristics to determine whether it’s legal to cast that spell.

Pegasus Guardian // Rescue the Foal — ruling 7

If a spell is cast as an Adventure, its controller exiles it instead of putting it into its owner’s graveyard as it resolves. For as long as it remains exiled, that player may cast it as a permanent spell. If an Adventure spell leaves the stack in any way other than resolving (most likely by being countered or by failing to resolve because its targets have all become illegal), that card won’t be exiled and the spell’s controller won’t be able to cast it as a permanent later.

Pegasus Guardian // Rescue the Foal — ruling 8

If an adventurer card ends up in exile for any other reason than by exiling itself while resolving, it won’t give you permission to cast it as a permanent spell.

Pegasus Guardian // Rescue the Foal : règles, fonctionnement et interactions (MTG)

Pegasus Guardian // Rescue the Foal 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

Flying At the beginning of your end step, if a permanent you controlled left the battlefield this turn, create a 1/1 white Pegasus creature token with flying. Exile target creature you control, then return that card to the battlefield under its owner's control. (Then exile this card. You may cast the creature later from exile.)

How it works : Pegasus Guardian // Rescue the Foal

Original English text — Wizards of the Coast / Scryfall

#1June 10, 2022· Wizards of the Coast
Pegasus Guardian's triggered ability will trigger even if Pegasus Guardian wasn't under your control at the time the permanent you controlled left the battlefield.
Card named in this ruling
Pegasus
#2June 10, 2022· Wizards of the Coast
When the card exiled by Rescue the Foal returns to the battlefield, it will be a new object with no connection to the card that was exiled. Auras attached to the exiled creature will be put into their owners' graveyards. Any Equipment will become unattached and remain on the battlefield. Any counters on the exiled creature will cease to exist.
No other card is named in this ruling.
#3June 10, 2022· Wizards of the Coast
If a token is exiled this way, it will cease to exist and won't return to the battlefield.
No other card is named in this ruling.
#4June 10, 2022· Wizards of the Coast
An adventurer card is a permanent card in every zone except the stack, as well as while on the stack if not cast as an Adventure. Ignore its alternative characteristics in those cases. For example, while it’s in your graveyard, Altar of Bhaal is an artifact card whose mana value is 2.
No other card is named in this ruling.
#5June 10, 2022· Wizards of the Coast
When casting a spell as an Adventure, use the alternative characteristics and ignore all of the card’s normal characteristics. The spell’s color, mana cost, mana value, and so on are determined by only those alternative characteristics. If the spell leaves the stack, it immediately resumes using its normal characteristics.
No other card is named in this ruling.
#6June 10, 2022· Wizards of the Coast
If you cast an adventurer card as an Adventure, use only its alternative characteristics to determine whether it’s legal to cast that spell.
No other card is named in this ruling.
#7June 10, 2022· Wizards of the Coast
If a spell is cast as an Adventure, its controller exiles it instead of putting it into its owner’s graveyard as it resolves. For as long as it remains exiled, that player may cast it as a permanent spell. If an Adventure spell leaves the stack in any way other than resolving (most likely by being countered or by failing to resolve because its targets have all become illegal), that card won’t be exiled and the spell’s controller won’t be able to cast it as a permanent later.
No other card is named in this ruling.
#8June 10, 2022· Wizards of the Coast
If an adventurer card ends up in exile for any other reason than by exiling itself while resolving, it won’t give you permission to cast it as a permanent spell.
No other card is named in this ruling.
#9June 10, 2022· Wizards of the Coast
You must still follow any relevant timing rules for the permanent spell you cast from exile. Normally, you’ll be able to cast it only during your main phase while the stack is empty.
No other card is named in this ruling.
#10June 10, 2022· Wizards of the Coast
If an effect copies an Adventure spell, that copy is exiled as it resolves. It ceases to exist as a state-based action; it’s not possible to cast the copy from exile.
No other card is named in this ruling.
#11June 10, 2022· Wizards of the Coast
An effect may refer to a card, spell, or permanent that “has an Adventure.” This refers to a card, spell, or permanent that has an adventurer card’s set of alternative characteristics, even if they’re not being used and even if that card was never cast as an Adventure.
No other card is named in this ruling.
#12June 10, 2022· Wizards of the Coast
If an object becomes a copy of an object that has an Adventure, the copy also has an Adventure. If it changes zones, it will either cease to exist (if it’s a token) or cease to be a copy (if it’s a nontoken permanent), and so you won’t be able to cast it as an Adventure.
No other card is named in this ruling.
#13June 10, 2022· Wizards of the Coast
If an effect instructs you to choose a card name, you may choose the alternative Adventure name. Consider only the alternative characteristics to determine whether that is an appropriate name to choose.
No other card is named in this ruling.
#14June 10, 2022· Wizards of the Coast
Casting a card as an Adventure isn’t casting it for an alternative cost. Effects that allow you to cast a spell for an alternative cost or without paying its mana cost may allow you to apply those to the Adventure.
No other card is named in this ruling.