Rule 702.168a

Disguise is a static ability that functions in any zone from which you could play the card it’s on, and the disguise effect works any time the card is face down. “Disguise [cost]” means “You may cast this card as a 2/2 face-down creature with ward {2}, no name, no subtypes, and no mana cost by paying {3} rather than paying its mana cost.” (See rule 708, “Face-Down Spells and Permanents.”)

Open rule in this release