Unlike a face-down creature that was cast using a disguise or morph ability, a manifested creature may still be turned face up after it loses its abilities if it's a creature card.
Bashful Beastie
If your library contains only one card when you manifest dread, you'll look at that card and put it onto the battlefield face down. You won't have the option to put it into your graveyard instead. If your library contains no cards when you manifest dread, you won't do anything.
If a manifested 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, as appropriate.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Aaron Miller
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
