Guardian Archon — ruling 1

In a two-player game, the chosen player won’t be much of a secret.

Guardian Archon — ruling 2

There are several ways to secretly choose an opponent. Perhaps the most popular way is to write the chosen player’s name on a piece of paper that is kept with Guardian Archon.

Guardian Archon — ruling 3

If you control more than one Guardian Archon, you may choose a different opponent for each one. Be careful to keep track of which opponent is chosen for each Guardian Archon.

Guardian Archon — ruling 4

If Guardian Archon leaves the battlefield and returns, it’s considered a new object. You may choose a new opponent and you may activate its last ability again.

Guardian Archon — ruling 5

If you didn’t choose an opponent as Guardian Archon entered the battlefield, you can’t pay the cost to activate the last ability. This will usually happen because you gained control of another player’s Guardian Archon or because a creature already on the battlefield became a copy of Guardian Archon.

Guardian Archon — ruling 6

Protection from a player means all of the following: (1) Neither you nor the target permanent can be the target of spells or abilities controlled by the chosen player. (2) Neither you nor the target permanent can be enchanted or equipped by any Auras or Equipment controlled by the chosen players. (Okay, Fortifications too, if the target permanent is a land.) (3) If the target permanent is a creature, it can’t be blocked by creatures controlled by the chosen player. (4) All damage that would be dealt to you or the target permanent by sources controlled by the chosen player is prevented. The same is true for sources owned by the chosen player that don’t have controllers.

Guardian Archon : règles, fonctionnement et interactions (MTG)

Guardian Archon 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 As this creature enters, secretly choose an opponent. Reveal the player you chose: You and target permanent you control each gain protection from the chosen player until end of turn. Activate only once.

How it works : Guardian Archon

Original English text — Wizards of the Coast / Scryfall

#1April 16, 2021· Wizards of the Coast
In a two-player game, the chosen player won’t be much of a secret.
No other card is named in this ruling.
#2April 16, 2021· Wizards of the Coast
There are several ways to secretly choose an opponent. Perhaps the most popular way is to write the chosen player’s name on a piece of paper that is kept with Guardian Archon.
No other card is named in this ruling.
#3April 16, 2021· Wizards of the Coast
If you control more than one Guardian Archon, you may choose a different opponent for each one. Be careful to keep track of which opponent is chosen for each Guardian Archon.
No other card is named in this ruling.
#4April 16, 2021· Wizards of the Coast
If Guardian Archon leaves the battlefield and returns, it’s considered a new object. You may choose a new opponent and you may activate its last ability again.
No other card is named in this ruling.
#5April 16, 2021· Wizards of the Coast
If you didn’t choose an opponent as Guardian Archon entered the battlefield, you can’t pay the cost to activate the last ability. This will usually happen because you gained control of another player’s Guardian Archon or because a creature already on the battlefield became a copy of Guardian Archon.
No other card is named in this ruling.
#6April 16, 2021· Wizards of the Coast
Protection from a player means all of the following: (1) Neither you nor the target permanent can be the target of spells or abilities controlled by the chosen player. (2) Neither you nor the target permanent can be enchanted or equipped by any Auras or Equipment controlled by the chosen players. (Okay, Fortifications too, if the target permanent is a land.) (3) If the target permanent is a creature, it can’t be blocked by creatures controlled by the chosen player. (4) All damage that would be dealt to you or the target permanent by sources controlled by the chosen player is prevented. The same is true for sources owned by the chosen player that don’t have controllers.
No other card is named in this ruling.