The blue glowing runic lines of the magic crest flow outward to cover the entirety of your body. You groan and thrash in your bed, futilely trying to escape the sensation of flames licking your skin. They are no longer warm, but they still heat up your exposed flesh until you're flush and beaded with glistening sweat.
Sensation and urges, both new and unfamiliar, are making themselves known with the force of an avalanche and buries your mind in a thick layer of viscous and sweet honey. You can feel your thoughts slowing to a crawl until you're driven more by instinct than conscious action.
Your white nails dig into the sheets as your back arches with a spasm. You are helpless and can only watch they pierce the cloth as they lengthen unnaturally with the trimmed ends tapering off into sharp points. And the skin around your hand harden and crack, turning into black and ridged scales that crawl up your arm until it resembles a pair of jagged, long-sleeved gloves. You can feel something similar running down your spine then splitting off, with branches running underneath your breasts, and crawling around your hips before weaving down the sides of your legs.
As the line of scales reaches your buttocks, you feel a pressure building at the base of your spine. It pushes outward, with the pressure widening as the reptilian tail growing out of your spine become thick and large. But like your nails, tapers, with the tip shifting into a phallic gland large enough to put the man you had been to shame. You let out a wordless, shuddering moan filled with desire as you watch it swaying between your splayed legs. The fear of what you're transforming into dimming, replaced with a growing thirst.
“GUARDS!” With an immense effort of will, you fight through the slow-moving fluid to call out to the two captors meant to keep you inside your room for the night. And your heart fills with hope at whatever is happening to you will end when you hear them scrambling to enter.
But that hope is dashed when you lay your gaze on them. In that moment, your eyes fill with darkness as your slitted iris begins to glow with a baleful fel green light. You can see their will leaving them, in real time watching their expressions slackening as they become enslaved to the creature you're turning into. They let their weapons clatter to the floor and begin to undress.
You try to push yourself away, but you stay as you're hit by the musky scent of their cocks. The two men crawl over the bed until you're face-to-face with their crotches and stiff members. Any hesitation you felt leave you as you swallow one of the cocks, pushing it deeper until you feel it hitting the depths of your throat. Once its slathered with your saliva, you switch and let your clawed fingers wrap around the wet length you so recently released. The pleasure they feel is something physical, and you feel it flowing into you with stroke of your hand or bob of your head.
You hardly notice as the elfin tips of your ears part the platinum blonde locks on the side of your head, and a set of horns do the same in the front. So consumed with your own pleasure and theirs. And as you take both cocks into your mouth at once, letting their glans mash up against each other and your eager tongue, your back arches again to complete the transformation and release the four bat-like wings emerging from your back.
It hits you at the same time as they start to pour cum down your throat which you greedily swallow until you've had your fill.
The light of the tattoos fade and blend into your blue skin.
Then something clicks in your mind and the changes you've undergone reverts, leaving you with the body of human princess instead of the transcendent form and beauty of a succubus. But it's only a superficial change.
You lovingly brush against the two cocks that fed you with a pair of your fingertips as you command the two men they're attached too to forget what happened and return to their post. Feeling drained, perhaps; they had been up guarding you all night after all. Full and happy you could easily go back to sleep and await the person coming to pick you up. But before you also didn't have the means to make any other choice than turning into a woman to be married off. Did you even care about the fate of your father's kingdom anymore, or was that something else you lost along with your humanity?
You pondered the endless choices before you as you lay in your cum-stained bed, smiling wickedly as you traced a path around your dripping sex with one of your fingers.