Guardian of the Forgotten

If a face-down permanent leaves the battlefield, you must reveal it. You must also reveal all face-down spells and permanents you control if you leave the game or the game end.

A permanent that turns face up or face down changes characteristics but is otherwise the same permanent. Spells and abilities that were targeting that permanent and Auras and Equipment that were attached to that permanent aren't affected unless the new characteristics of the object change the legality of those targets or attachments.

An Aura controlled by another player does not cause a creature you control to be modified.

A creature that is equipped is considered modified no matter who controls the Equipment that's attached to it.

Turning a permanent face up or face down doesn't change whether that permanent is tapped or untapped.

If something tries to turn a face-down instant or sorcery card on the battlefield face up, reveal that card to show all players it's an instant or sorcery card. The permanent remains on the battlefield face down. Abilities that trigger when a permanent turns face up won't trigger, because even though you revealed the card, it never turned face up.

Because face-down creatures don't have a name, they can't have the same name as any other creature, even another face-down creature.

You must ensure that your face-down spells and permanents can be easily differentiated from each other. You're not allowed to mix up the cards that represent them on the battlefield to confuse other players. The order in which they entered the battlefield should remain clear, as well as what ability caused them to be face down. (This includes morph, manifest, disguise, cloak, and a few other effects that turn cards face down.) Common methods for doing this include using markers or dice, or simply placing them in order on the battlefield.

Unlike a face-down creature that was cast using a morph or disguise ability, a manifested creature may still be turned face up after it loses its abilities if it's a creature card.

If a double-faced card is manifested, it will be put onto the battlefield face down. While face down, it can't transform. If the front face of the card is a creature card, you can turn it face up by paying its mana cost. If you do, its front face will be up.

If a manifested creature would have morph or disguise if it were face up, you may also turn it face up by paying its morph cost or disguise cost.

A creature with a counter on it is considered modified no matter what kind of counter it is or which player put it on that creature.