After reaching the final stage and defeating Azazel, you would notice that the Rectifier of All Things self-destructs because of its weakened state, leaving a glass ball of darkness inside of it. It then drops and rolls toward you, stopped at an inch of both feet of yours. Curious and intrigued about this, you reach a hand to pick the ball up, only for an unknown power to consume you. Two feathered wings emerge from your back, your fingers turn into sharp claws, your skin turns into a dark hue, and two horns emerge from your top of your head. You also had a third eye manifested on your forehead, allowing you to shoot lasers from it (You now have Devil's blood) The Devil Gene has permanently latched onto your skin, forming itself on your left shoulder