A nonmodal double-faced card enters with its front face up by default, unless a spell or ability instructs you to put it onto the battlefield transformed or allows you to cast it transformed, in which case it enters with its back face up.
Dion, Bahamut's Dominant // Bahamut, Warden of Light
Dion's first ability will still give it flying during your turn even if Dion somehow isn't a Knight.
If you are instructed to put a card that isn't a double-faced card onto the battlefield transformed, it will not enter at all. In that case, it stays in the zone it was previously in. For example, if a single-faced card is a copy of Crystal Fragments, it will be exiled during the resolution of its second ability and remain in exile.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Kevin Glint
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
