Unexplained Absence

If a face-down creature loses its abilities, it can’t be turned face up with a disguise ability because it will no longer have a disguise ability (or a disguise cost) once 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.

Because the permanent is on the battlefield both before and after it’s turned face up, turning a permanent face up doesn’t cause any enters-the-battlefield abilities to trigger.

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 disguise, cloak, and in games involving older cards, morph and manifest, as well as 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.

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

To cloak a card, put it onto the battlefield face down. It becomes a 2/2 face-down creature card with ward {2} and no name, mana cost, or creature types. It’s colorless and has a mana value of 0. Other effects that apply to the permanent can still grant it any characteristics it doesn’t have or change the characteristics it does have.