The demon appears in the circle like an explosion in reverse. A globe glowing metaviolet with arcane energy as it shrinks in, faster and faster until it abruptly collapses into a demon-shaped volume. There's a small puff of displaced air that makes the assorted papers scattered around Kae's room flutter a little bit as the energy incorporates into a demon. Crimson skin, black-and-yellow eyes, a three-foot spaded tail, and short black hair that comes down to her shoulders, matching the only bit of clothing she's wearing: black leather knee-high boots with yellow trim. Pretty standard stuff. The dick between her legs is a little unusual (and either the process of being summoned turns her on, or she's just always hard), but Kae doesn't particularly mind. Certainly she can empathize. If anything, she's a little jealous of the size.
The summoning grid tells her that the closest pronunciation of the demon's name that she can actually speak with her short tongue and mortal throat is /tɛrə/ so she puts on her best Serious Business Mage voice, holds up her hand with her palm facing herself, and says "In the name of Lilith the First and all Her spawn: I, ■■■■" (stumbling over that name, fluctuations in the ambient aether), "bind you, Tera, to my service until I release you or your service is complete."
Once that's done, her voice softens and she pulls a glass sphere, maybe half the width of her hand across, out of the pocket of her black robes. There's a light blue glow inside, swirling around almost like smoke being blown around and around by wind. "My offer is this. A year of my spare mana for you resculpting my body."
Tera eyes the girl that summoned her. Black robes, plain brown hair, blue eyes. Tall for a girl, and the structure of her body doesn't quite match what she knows about human anatomy. There's a glamour on her chest as well, which makes sense, given the nature of the request. It's a very good glamour; she has to squint a little with her second sight to see it. She takes a couple steps forward, hips swaying (she's not trying to seduce Kae [yet], honest, it's just a thing that succubi do) and takes the orb from her.
She holds it with the very tips of her fingers as she lifts it in front of her face. Her irises glow for a moment, head tilted slightly to the side... before she drops it. Kae flinches at the noise of it hitting the ground, but instead of breaking, it just rolls to the side.
"I said, not enough. There's maybe twenty, twenty-five kilothaums in here and the sort of changes I'm guessing you want would easily take a couple hundred."
"But I haven't even told you what I want!"
"You're not the first mage with a fucked-up hormone balance that wanted bodysculpting from a demon."
"No, that's not possible, there has to be something you can--"
"Look. Which one of us is the demon here? Permanent natural body alteration is hard. You can't cut corners with this stuff, you'll get sculptor's bane and your body will grow itself to death. It's a painful way to go. Even if I didn't charge the twenty-five percent fee and I drained myself to discarnation, I couldn't do it."
Kae stands there, eyes going back and forth between the orb and the demon. Then she crouches down and buries her hands between her knees. She doesn't cry, but she opens her mouth and closes it a couple times, trying to find what to say. It's like looking for hay in a haystack.
Tera looks down at her with her arms crossed over her stomach, tail flicking around behind her. ... yeah. She'll definitely do.
"I think I can still help you."
"But you said that it wasn't enough."
"And it's not. How much do you know about how succubi reproduce?"
"Well, I know vice demons generally show up where the origin plane is full of one emotion, and that--"
Tera waves a hand. "Right, yeah, war creates wrath demons, that sort of thing. Almost right. But there's one other way that you probably didn't learn about."
Ideas flit through Kae's head, but one of them stands out. "You turn mortals into more of yourselves."
"See, it's exactly that sort of amazing intellect that makes you a prime candidate."
"Oh, fuck off."
"And that wit!"
"Are all succubi assholes, or did I just get lucky?"
"I'm giving you the opportunity of a lifetime, the chance to get the thing you want most in your life. You're telling me to fuck off. And I'm the asshole?"
Kae pauses, takes a moment to collect herself, then stands up. "Fine."
"What's your truename?"
Kae winces a little at the question. "It's, uh, ■■■■. Like I said during the binding."
Tera shakes her head. "Funny, you don't look like a ■■■■ to me." A dismissive wave of her hand, a roll of her eyes. "Actually. That'd explain why your mana was so weak. You were using that name for your rituals?"
"Um, yeah? It's what they bound to the ring when I registered." She holds up her right hand, index finger extended slightly to highlight the featureless silver ring wrapped around it.
"Yeah, that's the problem. It's a name, but it's not your name, so the connection's only barely there. Like trying to drain a tub through a straw. What's your real name?"
There's a moment before comprehension dawns on her face. "Oh. Oh! It's Kae." She smiles a little when she says it.
"Kae." Tera concentrates on the name as she says it, and she can see the little ripples of aether get drawn in towards the mage. "Yeah, that definitely feels like you. So! Are you ready?"
"Wait." Kae holds up her hand in front of her. "First, I need to know you're telling the truth."
Tera nods and holds up the palm of her hand facing herself, eyes closed. There's electricity in the air, and Kae's own second sight shows faint blue flames surrounding the demon's body. "In the name of Lilith the First and all Her spawn: I, Tera, swear that the incantation I will provide you, Kae," (a shiver, a thrill), "will transform you into a succubus as I have described, nothing more and nothing less." Then her eyes open again and the magic dissipates. "Happy?"
"Very." She's trying to suppress it, but there's a grin on her face.
"Alright. We need a... I think you call it a five-point Volger-Ka circle in order to work the soulsculpt and capture the energy. And I left all my runic ink in my other pockets."
Kae walks over to a messy table and picks up three unlabeled bottles of ink. There's a little chill as she steps through the barrier of the summoning circle, but it recognizes her as mortal and lets her through. She hands the black ink to Kae, who traces a circle about as wide as her armspan on the floor inside the summoning circle; Kae follows up behind her, inscribing silver runes in Thaumic on the floor.
"Lie down in the center with your head, arms, and legs at the points."
"Should I leave my clothes on?"
"Well, I'd like to fuck you afterwards, and that'd make it kinda hard."
Kae grins and unwraps her silver robe, shrugging it off her body and letting it fall into a pool of fabric on the ground away from the circle. Which lets Tera get a good look at her for the first time: her chest isn't anything to write home about, but her dick looks pretty nice even if she's not hard (yet). Her skin's got the telltale tiny black dots of someone who's scrupulous about shaving, but it's not quite enough. She notices the demon checking her out and shakes her ass a little, and Tera gives it a teasing little smack in response.
Kae giggles and gets down on all fours, tracing her hand above the rune circles and sealing the ink into place, then lies down in the position Tera showed her. Tera's hands grab her arms and move them around a little, then her legs, and finally her head. "Last chance to back out. Once this actually starts, stopping it's gonna be ugly."
"Well, I wasn't sure before... but you said you were gonna fuck me."
Tera just smirks in response and snaps her fingers. Glowing purple manacles wrap around Kae's wrists and ankles, and a blue collar emerges from the floor and encircles her neck, binding her in place with short chains of mystical energy. She struggles a little against them, but only to test how much give they have (none at all, as it turns out); she has no intention of leaving.
Tera's claws trace lines over Kae's skin, leaving behind runes that briefly glow a bright blue before fading into metaviolet. Kae isn't an expert sculptor, but she can tell that Tera is deliberately taking her time with the process, going over areas that had already faded pale blue and tracing over the invisible symbols in her skin. She can see Tera's own runes glowing in the process, thick lines and curves that decorate her entire body and guide her mana from her center, through the tips of her fingers, and into Kae's body.
Her nails are sharpening as well, turning darker and darker and darker from their old fleshy color until they're a solid black and sharpened to a point. She curls her fingers in and out as if she's trying them out for the first time, and she turns her head to the side as if to make sure that yes, this is really happening to her. It just makes her more nervous, more thrilled
She can feel her soul burning with black flame as the tenebrous tendrils of Tera's will work their way through. The air inside the circle is thick with magical energy, and with each little bit of her skin that turns pale blue she can feel herself absorb it. Not only is she becoming demonic, she's becoming stronger. It feels like the introduction to the best orgasm she's ever had. But she stays focused on her body, imagining the self she wants.
Her chest grows out, of course. Kaer ripples and coalesces in her body, transformed into more of herself, pushing out from her chest and leaving her deliciously sore. Tera briefly moves one hand to play with her growing breasts and the sensation of them moving up and down on her chest feels absolutely wonderful. She focuses on the size she wants: not unrealistically big, but big enough that she'll definitely get noticed (well, the color of her skin and the aura of lust she'll exude would probably do that anyway).
Next up is her bodyshape. Her entire body shrinks a little as words she doesn't understand flow from Tera's mouth (ikai ikai ephad zu parnev ukt). The demon's moved her attention over to her left arm, giving it the same soul-searing treatment as the right. Her right arm is still tingling, but she can tell that the excess of mana stored in it has almost run dry, which must be why Tera's switched sides. A couple inches disappear from her arms and legs, making the bindings shift around to keep her pinned in place without stretching her, and the succubus on top of her has to move around to properly continue the ritual. But when it's all done, Kae is still a couple inches over average height for a girl. She didn't mind being tall, after all.
Then her voice. She worked hard to train herself pitch it up in just the right way, but with the power coursing through her veins she just reaches out and shift her vocal cords directly. Tera sees what she's doing out of the corner of her eye; the flow of mana is brightest around her throat. So she moves her head to nibble and kiss and suck on one of Kae's fingers so she can hear the shifts for herself. Music to both of their ears.
And, of course, the body hair. Both of the demon's hands caress Kae's body, watching her erase all of the hair she finds down to the very root. She takes the opportunity to play with Kae's breasts a little. "You really do wanna look like a sex demon, don't you?" she murmurs, and when Kae opens her mouth to reply she pulls her into a deep, crushing kiss. Her hands roam over Tera's back as they continue, eradicating the signs of a self that she'd never asked for, and Tera's tail goes down to wrap around and cleanse Kae's legs. The three limbs meet in the middle, hands grabbing Kae's ass as the spade of the tail strokes over her balls and wraps up her cock, stroking it up and down a little, making her whimper and squirm just a bit.
"You know, you're kinda cute like this... part human, part succubus. You're finished changing yourself, right?"
"Mm... yeah." It's hard for Kae to see herself with Tera's gorgeous body in the way (and Tera can almost taste the lust pouring off of her, driving her wild; if Tera didn't say she was going to fuck her she would beg) but she can tell just from thinking about it her self-image that her new body is perfect.
"In that case, I don't have to keep changing you. You could just stay like this, human enough to pass with a little camouflage. I'll teach you enough lightbending so that nobody would ever have to know that your soul's been..." and here Tera leans down to bite her neck, "tainted."
"Or instead." Another bite, and Kae has to hold herself back from moaning. "I could finish this ritual, make you completely and utterly one of us. Give you a new purpose in life, one devoted to sex and pleasure and just feeling as good as you possibly can. But there won't be any turning back, because no matter what you do, anyone with even a hint of mage-sight will be able to tell what you are."
It takes Kae a few breathy moments in order to compose herself enough to reply. "Y-you know what I want."
One hand slides down Kae's chest, leaving a narrow slash of corrupted blue skin on its way down between her legs, fingers wrapped around her cock and stroking it up and down a few times. The other hand rests atop her chest, pinching a nipple between her fingers and making Kae whimper. "I want to hear you say it."
"S... nngh, say what?"
"What you want me to do to you."
"I want--", another pinch, another squeeze, another moan, "I want you to completely turn me into a succubus."
"Really?" Tera starts stroking up and down, up and down. When she squeezes the nipple harder, Kae moans out and arches her chest up, thrusting her hips into Tera's grip. "Because I'm not convinced just from that little display. In fact..." Tera takes both of her hands off of Kae's pleasure-tortured body, leaving her writhing on the floor in her bondage. "I don't want anyone to be able to say I was influencing you through my touch." Kae whimpers a little, trying to reach up and somehow force Tera to continue stroking her, but her ethereal restraints hold fast. "So. I'm not going to touch you again until you tell me just. how. badly. you want me to do this to you."
"I... I need you to finish the ritual, please! This is the best I've ever felt in my life, and you have everything I've ever wanted! I need this power, I need to be filled with lust and desire so I can wrap the world around my finger!" Kae's thrusting into the cool air, cock twitching and the occasional drip of pre sliding down the underside. "I'd do anything for this power, please, just finish me! Complete me! Make me... make me whole!"
Tera grins so wide that Kae almost thinks that she's about to be devoured. "Good girl." And then she gets back to work, ik vai od vard phenektria akte, chanting power into Kae's hears. Those slender fingers wrap around both of Kae's breasts and give them a firm squeeze, making Kae cry out "f-fuck!" in pleasure. The intensity of their transformation made them sensitive, and the blue spreading from the captive girl's arms doesn't exactly help. Tera dips her head down to bite and tug and suck at Kae's left nipple, then her right, and it makes her breath quicken. Nails dig into her flesh, just shy of making her bleed, torturing her with the ecstasy of her contact. By the time Tera's done, Kae's chest is a light shade of blue, and her nipples and areolae darken and darken until they're almost pure black; the contrast only serves to draw more attention to her tits.
Wild fantasies flash through her head as Tera gets to work on her hips, imagining herself at the center of attention, seducing everyone she meets to draw them under her control. It makes her hiss in delirious pleasure when Tera's claws trace down to her hips and her thighs, covering her in more and more of those invisible runes of power. The corruption wraps itself around her cock, spiraling up and up and making it more and more sensitive with each inch that it consumes, until Kae almost climaxes when it reaches the very tip. And then Tera moves her head down and gives the base a firm squeeze as she kisses the underside and she paints her blue chest white, her breath caught in her throat from her first mind-blowing orgasm in her new body. The pleasure only speeds up her transformation, makes the tide of her new skin rush faster and faster down her legs until her toes end in the same sort of pointy claws as her hands.
The crimson demon gets back to work kneading her ass next. At first there's an itch she can't scratch at the base of her tailbone, and she grinds her hips into the floor trying to satisfy it. But the itching keeps growing until eventually she feels something push out of her body. She can't see it, but she knows it has to be her new tail. The muscles are completely unfamiliar to her, but it turns out that that doesn't matter because Tera lifts her back up just enough to tug it out to the side so she can bind it to the floor as well.
Tera crawls back up her body to look her in the eyes; her head is the one part of her that's still human. "Are you ready to leave your old life behind?" she purrs, even though she full well knows the answer that she'll get.
"That's what I like to hear." A snap of Tera's fingers and a quick incantation under her breath and Kae's legs lift up on their own, the chains that bound her now fastened to thin air a good couple feet off of the floor, exposing her ass. Tera gives her pale rear a smack with her hand, making sure to really dig in with the tips of her fingers. The pain feels like pleasure, makes her moan, makes her grind against those claws. So Tera gives the painslut what the she wants: another smack on the other side, and then another. A hard squeeze.
Kae watches Tera grind her dick between her legs, and her hips rock in time with the other demon's motions. "Mmmnhh... no lube?"
Tera smirks. "What kind of sex demons would we be," (and just the emphasis on that one word sends a thrill up Kae's spine from the base of her tail), "if we weren't always ready to fuck?" She illustrates her point by rubbing the spade of her tail over Kae's cock, which she realizes never went soft even after her orgasm. And her libido rises up again far quicker than it ever did before after an orgasm. And she's enjoying that tail rubbing up against her instead of feeling aching and sensitive like she normally would.
She's so busy grinding her throbbing cock against the tail that she's completely unprepared for when Tera sinks every last inch inside her in one thrust, and she yells out "F-fuck!". The shock of it spreads the corruption up her neck, little crimson flames of transformation tickling at her jawline. But she was right; it didn't hurt or feel dry or anything. She doesn't get too much of a chance to think about it, because soon the demon's starting to build up a slow rhythm in and out of her body, leaving her breathless.
Even though the magical chains hold her legs firmly in mid-air, Tera's still holding on tight to her ass for more support as she thrusts in and out, in and out, in and out. She starts slowly, but quickly builds up a fairly steady pace matched by the speed of her tail stroking up and down Kae's cock.
The corruption continues to spread up her head, first licking over her lower jaw and then transforming her incisors to points almost as sharp as her claws. The tip of her tongue splits in two just a little bit; it doesn't hurt any more than the rest of her transformation, but the feeling of twin tongue tips rubbing against the inside her teeth is strange and unfamiliar, especially given that her tongue feels a couple inches longer now. She has to open her mouth to let it spill out over her chin. Her upper teeth sharpen next as the crimson claims them, and her ears become quite a bit pointier as they're adjusted.
The sight of it is too much for Tera; with her right hand still firmly holding Kae's ass in place so she can fuck it, her left hand slides up the small of her back, past her tail, and cradles the back of her head as she leans down for a kiss. Tera shoves her tongue in Kae's mouth, wrapping it around hers, licking and sucking and pulling back to nibble on her pink lips. And being up close gives her a nice view of Kae's eyes changing: splotches of yellow in the white sclerae that grow and merge, even flowing over her old irises, leaving just a cat's-eye slit of black in the middle.
By this point Tera's far too distracted by getting fucked to actively focus on her morphology, so the changes washing over her body are just her subconscious focusing on what she thinks a demon looks like. So her dark-brown hair shifts even further towards black and grows another couple inches until it comes between her shoulder blades (or, it would, if it wasn't pooled beneath her in her current pose). And one the last few bits of her skin hidden beneath her hair are changed, her entire body tingles as if in a reminder: this is her now. This is what she is. This is what she begged to be.
"You're beautiful." Tera murmurs as she pulls her mouth back from the kiss, slowing down her pace a bit so they can talk.
"You're just saying that because I'm, mmn, a demon now."
"So? That doesn't make it any less true." Tera leans down to bite at Kae's neck and sucks hard, tongue rubbing up against her skin as if tasting the soul she'd just stained black. Her hips slow down their pace a bit, then speed up, harder and more insistent than before. "Fuck, I'm gonna come... you want it in you or on you?"
"On me, so I can, nnh, taste it."
Tera's all too happy to oblige; her hips draw back after a few more hard thrusts, and she wraps her hand around her cock, making wet noises as she strokes it up and down, tail still working Kae's cock over. And before long, she lets out a loud moan as her orgasm hits her, painting Kae's stomach and the underside of her tits white with her release; a few ropes even land on her thighs.
Not only does Kae love the sight of the succubus cumming on her, but she can taste Tera's orgasm now, and it's absolutely delicious. It's like the best meal she's ever had, dinner and desert all rolled into one salty-sweet-tangy sensation that caresses her tongue. It only takes a few more strokes of Tera's tail before her own sticky white cum spurts all over both her newly-endowed chest and the runes on the floor, leaving her smooth skin looking messy.
Tera's left panting once she's ridden out her climax, but she does lean in a little to grind her cock against Kae's. And even though she just came, it still feels good; the immediate need for sex is gone, but the erotic intimacy is still nice, like a nap when she's not tired. A wave of the crimson demon's hands and the ethereal bindings holding Kae in place disappear; the first thing she does with her freedom, of course, is clean up her chest and breasts with two of her fingers and lick them clean. It's salty, of course, but with a bit of extra warmth as well. And with her newly-heightened senses, she could swear that she can taste the demonic essence.
Suddenly, Tera winces. "... Kae?"
"You didn't dispel the warding runes before you entered the circle, did you?""
"Well, they're succubus-patterned, so you're stuck in here just as much as I am now. How much did you put in 'em?"
"Shit. Uh... maybe five hundred?"
"Five hundred, and this looks like a class three, so fifty an hour... looks like we're stuck here for a while."
"That's alright.", Kae says as she gives Tera a little squeeze. "I think I'll manage." Tera responds by smacking the inside of her thigh a little with the spade of her tail, but the new succubus just giggles in response. Kae does her best to curl her tail around Tera's, but her inexperience means that she just sort of winds up flailing it around a little.
"Sleeping on top of someone isn't nearly as comfortable as you think. The tits tend to get in the way."
"Oh, shut up." Kae yawns and rolls onto her side, taking Tera with her. "'m tired."
"Getting your morphology rewritten takes a lot out of you." Tera yawns as well and smiles a little as she looks into Kae's eyes with a warmth contrasting her utterly cock-sure attitude when she was corrupting her. One hand plays with her chest a little, fingers bringing a quiet moan from Kae as they pinch her nipples, before her hand drops down to idly rest on her ass. "So does rewriting someone else. Looks like we're not sleeping in beds tonight."
"Mmm. Like I said, I'll manage." Kae gets as close to Tera as she can; the room seems colder now, or maybe it's just her increased body heat. She doesn't know what the future holds: can she still attend school? Can she still live here? But for now, it's enough to finally be happy with herself, and she gets the feeling that Tera will be more than happy to keep 'helping' her adjust to her new existence.
She can't wait.