You could not remember exactly how, but you once stumbled upon an article about succubi. They looked human for the most part, except for their wings, horns and tail. Surviving they do by feeding on males. They fuck them, and suck their energy out.
You became interested in the study of these creatures. You could even say you were slightly obsessed by them, as you once dreamed about being one. Why would you not become one yourself? It couldn't be that hard with your new powers, could it?
"Okay, here goes!", you said cutely as you prayed for the transformation to end well.
For a short while, it seemed like nothing was happening, but then you felt a sharp pain at the top of your massive butt. Looks like the tail was first to appear
"Owowowow, this hurts! But I'm sure it'll all be worth it in the end!".
The black, sharp tip of your tail had poked through your skin, and the typical spade shape followed suit. The hardest, and most painful part of the growth of your tail was now done. It didn't take very long for the rest of the tail to appear. Your nervous system changed, elongating your spinal cord.
"Wow, I can control it now! This feels so... weird! As if I have grown a new limb!"
You guessed it to be around 8 feet tall and and two inch thick on average. You did not have much time to try out it's functions, because you could feel a new pain, in your forehead this time.
"It's hurting again! I must stay strong and resist the pain!"
Two small bulges appeared, slowly growing outward. At one point, your skin was stretched too much and got pierced by two black horns. They were sharper than a knife and judging by the amount of light they reflected, they looked as if they had just been polished. They kept on growing until they were about 5 inch long, and 2.5 inch thick at the base. You didn't think you would really need them, but they felt like they could pierce through even diamond.
But once again, you did not have much time to try out your new horns, because the final change started happening.
Your shoulder blades reformed to be able to hold wings. Just like with your horns, bulges started appearing, and soon, your skin started to rip as it couldn't hold the pressure of the growing wings. The wing bones were black, just like your tail and horns, but the actual wings were a dark shade of purple. It took a while to get to the correct size, but they evenutally stopped at, you guessed, a 14 feet total wingspan.
You looked into the mirror and a demoness more sexy that you had ever seen on any drawing or picture. Your new additions made you look much more tough, yet at the same time they made you look cute and attractive. You loved it
"This seems perfect so far. What to do now.."