As your body was overwhelmed with excruciating pain you saw black scales growing across your arms, and shoulders, and at the same time red ones spread across your chest. Suddenly your spine cracked causing you to drop down on all fours. As the scales continue spreading the areas that they covered began changing. Your skeleton began changing expanding to the size of a horse as the scales spread up your arms. When the scales reached your hands you saw your thimbs retract into your palms, and your hands became large razor sharp claws. The scales then proceeded up your neck, and you neck lengthened, and cracked became long, and more movable. The scales then moved to your head, and all of your hair fell out as your skull reshaped forming a muzzle, and horns, and removing your ears, and nose which were now slits. Then the scales covered your back, and you roared in pain as your wings grew in, and thew were as each was as big as your body. You suddenly then felt tugging on your penis, and your form became slender, and you looked down to see your penis pull inwards leaving behind a moist vaginal slit. The scales then proceeded to change your feet which became 3 digit claws, and finally your tail grew in, and you roared when it did at the shear pain of it.
You knew now that the transformation was over, and you had the body of a female dragon. You had the thought to confirm your gender by poking at your new slit, but you couldn't feel anything in your nethers which was proof enough. You were traumatized overall, until you felt what seemed like thousands of thoughts, and memories poured into your mind. For some reason you couldn't recall any of them, until a figure appeared before you that looked exactly like you. "Hello, if you are hearing me then you are my reincarnated self. In other words you were once me, and you are currently confused over the transformation. My memories will become yours, and will be restored over time, but all you need to know now is that you are Twilight, legendary dragoness of flames, and darkness, representing the sun, and moon, or day, and night. That is all I can tell you, you will not see me again, goodbye, and good luck." The dragon said before a bright light filled the void, and you appeared.....
(This story has a Medieval/ fantasy setting)