Kuja, Genome Sorcerer

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

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.

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.