Kuja, Genome Sorcerer

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.

A token that is created as a copy of a double-faced permanent or a double-faced card in another zone is a double-faced token. It will have both the front face and back face of whatever object it's copying. If it's copying a double-faced permanent whose back face is up, the token will enter with its back face up. It can transform if instructed to do so.

Each face of a nonmodal double-faced card has its own set of characteristics: name, types, subtypes, abilities, and so on. While a nonmodal double-faced permanent is on the battlefield, consider only the characteristics of the face that's currently up. The other set of characteristics is ignored.

Each nonmodal double-faced card in this release is cast face up. In every zone other than the battlefield, consider only the characteristics of its front face. If it is on the battlefield, consider only the characteristics of the face that's up; the other face's characteristics are ignored.

If another effect (or effects) modifies how much damage a Wizard you control would deal—by preventing some of it, for example—the player being dealt damage or the controller of the permanent being dealt damage chooses the order in which any such effects (including Trance Kuja's) apply. If all of the damage is prevented, Trance Kuja's effect no longer applies.

If damage dealt by a Wizard you control is being divided or assigned among multiple permanents and/or players, that damage is divided or assigned before doubling. For example, if you attack with a 4/6 Wizard with trample and it's blocked by a 1/1 creature, you can assign 1 damage to the blocker and 3 damage to the defending player. Those amounts are then doubled to 2 and 6, respectively.

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.

In the Commander variant, a double-faced card's color identity is determined by the mana costs and mana symbols in the rules text of both faces combined. If either face has a color indicator or basic land type, those are also considered. For example, Cecil, Dark Knight's color identity is black and white, since its front face is black and its back face has a white color indicator.

The Wizard token's ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered or otherwise leaves the stack.

The back face of a nonmodal double-faced card usually has a color indicator that defines its color.

The damage is dealt by the same source as the original source of damage. The doubled damage isn't dealt by Trance Kuja unless it was the original source of damage.

The mana value of a nonmodal double-faced card is the mana value of its front face, no matter which face is up.