The mana value of a transforming double-faced card is the mana value of its front face, no matter which face is up.
Befriending the Moths // Imperial Moth
A transforming double-faced card enters the battlefield with its front face up by default, unless a spell or ability instructs you to put it onto the battlefield transformed or you cast it transformed, in which case it enters with its back face up.
If you are instructed to put a card that isn't a double-faced card onto the battlefield transformed, it will not enter the battlefield 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 Azusa's Many Journeys, the chapter III ability will cause it to be exiled and then remain in exile.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Matt Stewart
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
