Chapter Text
Caster could hardly believe her luck. When she was summoned as part of the Fifth Holy Grail War, her original master was so horrible the sorceress outright killed him, preferring to die than to serve him. Thankfully, she soon ran into Souichirou Kuzuki. Though he was a very, very stoic man, he felt sympathy for her, and despite not being a Mage, entered into a pact with her to keep her bound to this plane. In exchange, she enhanced his amazing fighting skills, crafted from back when he was an assassin, to become an extremely deadly fighter.
Souichirou had no real plans on what to do with the Holy Grail, and as such, left up all the planning to Caster. He was such an honest and pure gentleman, despite his emotionless demeanor, that the witch soon fell in love with him. In the event she won the Holy Grail, no matter what else happened, she was determined to have him by her side forever.
However, to win the Holy Grail War, she would need even more of an edge. Though he was strong, Souichirou was not a Magus, therefore couldn't use his mana to fuel Caster, requiring her to siphon it from random people. While she technically does have access to unlimited magical energy, thanks to coming from the Age of Gods, the limitations brought on by the Holy Grail War has neutered her power. Caster's first step to solve this was by summoning a Servant of her own, an Assassin-class named Sasaki Kojiro, who guards their home base of the Ryuudo Temple. Though he didn't have the full abilities of Assassin, he was still extremely strong.
That was when she saw who she really wanted to push her over the edge: Saber.
Known in her past life as Artoria Pendragon, King of Britain, she had been summoned as the Saber-class servant of a boy named Shirou Emiya, who just so happened to be a student in Souichirou's class. Observing the boy, Caster found something delicious. He was completely inept at Magercraft. He had some minor skill, yes, but it was obvious had never been truly tutored in it, meaning his pact with Saber was extremely limited.
That works out just fine for her.
Kidnapping a woman by the name of Taiga Fujine, one of Souichirou's co-workers and who hangs out with Emiya often, Caster ambushes Shirou, Saber, and another Master, Rin Tohsaka, on a bridge. The terms were simple: Exchange Saber for Taiga. Shiro's pained expression was so delightful to witness, as well as his eventual breakdown when he agreed to the terms. Casting Fujine aside, the sorceress pulled out her Noble Phantasm, the Rule Breaker dagger, which allowed her to cancel out a Master/Servant contract. After stabbing it into Shiro, Caster transferred the contract with Saber to herself, gaining her Command Seals. She then let the humans go, warning them not to interfere in her plans, before vanishing with Saber.
Now, Caster had her short-term prize helpless before her. While Saber was technically contracted to Caster, she was still of her own free mind and will. Her loyalties still lied with Shirou and Rin.
She needed to change that.
Back at the temple, Caster had Saber dressed in a flowery white dress, hands bound, with a magic circle beneath her. She was currently bent over, struggling with all her might to resist Caster's spell.
“Come now, dear Saber. How much longer do you think you can hold on?”
Saber could only grunt, the strain taking its toll on her body.
Because of Saber's high innate Magic Resistance in her body, Caster needed to break it down in order to fully take control of her. Luckily for her, she knew how to do so in the most delicious way possible.
“I must say, Saber, you really are quite the fetching specimen.” Caster purred, trailing her fingers along Saber's bare back, “Your pained face, your strained body, your delicate figure. Why, it's all so, so perfect. I could just eat you right up!”
Saber grunted again, “Shirou will... come for me... you witch!”
Caster frowned. She hated being called “witch.” Raising her hand, electricity crackled around Saber, causing her to cry out in pain.
“I will teach you how to properly respect your new Master. For instance, if you obey me, I will make sure you feel much more pleasurable.”
She reached down and pulled down the front of her dress, cupping Saber's small breasts. The former king whimpered as her body was groped. A part of her had fallen for Shirou, but she hadn't really sorted her feelings about that when she was kidnapped. Now, she was being sexually assaulted, shame welling up within her.
I am the former King of Britain! King of Kings! I cannot allow myself to succumb to this foul treatment!
But Caster's fingers knew what they were doing. Her fingers traced along the curves of her breasts, and while she didn't have a large chest, she still had mounds to grope and mash. Saber found herself struggling as she tried to tell herself the ministrations didn't feel good to her.
Caster was humming away, unable to get enough of Saber's chest. She could spend hours doing nothing but manipulating those cute breasts. She saw how erect Saber's nipples were and decided to pinch them, delighting in how much it made her victim squeal. Leaning underneath Saber, Caster flicked out her tongue and began to lick and suck on the teats.
“Mmm, you taste splendidly, my little pet.”
Saber could only groan.
“Oh? Sounds like you're enjoying this. Let me continue, then.”
Her eyes bulged as Caster continued to lick her boobs. She couldn't even form a reply, as it was taking all her mental resistance to not moan from all the attention. Her cheeks were flushed with arousal, and she could feel Caster's spell worm its way into her body.
If I submit, I can feel this good...
No, wait! That's not me! I cannot give in!
Saber prayed that Shirou and Rin could come up with a plan to save her soon, because she had no idea how much longer she could hold out.
Eventually, Caster decided to remove herself from the blonde woman's chest, “My, you certainly are crumbling fast, my dear. I wonder how much quicker you'll fall if I speak to your other mouth?”
Realizing what she meant, Saber's eyes went wide and she renewed her struggling, desperation overtaking her.
“Do not touch me there! I will...!”
Saber felt her dress lift up and around her hips. With her already bent forward and her legs spread, her lack of panties made the view from Caster's eyes all the more enticing.
“Mmm, Saber. You put up a front of a strong, stoic soldier, but a little groping and you're gushing wet! You little pervert, you!”
Humiliation raced through Saber's body. She didn't know how much strength she had left already, but then she felt one of Caster's fingers rub her slit and she gasped, pushing her hips away. Caster only laughed, enjoying the resistance. But Saber couldn't exactly move very far, so Caster resumed rubbing her pussy lips, causing unending waves of pleasure to ripple through Saber's body.
Then, Caster decided to remove her gloves and stick two fingers inside, and Saber squealed despite trying to hold her tongue in. That only encouraged her captor even more. Her fingers explored Saber's inner sanctum, rubbing her walls. With a little bit of magic, she was able to enhance her touch, making Saber even more aroused. She felt her prey's knees buckle and smiled before continuing.
Panic raced through Saber's mind. Caster had only poked two fingers inside her, but arousal was engulfing Saber's soul. Her legs were wobbly, turning into jelly faster by the second. Saber's face was red with shame, humiliation, and arousal as she was openly panting now. She tried to refocus the best she could, but something building up inside her refused to allow it.
“Saber, you're gushing so much! Why do you keep lying about how your body feels? It's obviously begging you to truly become mine!”
No! No, I have to hang on! Please, Shirou. I can't hold out much longer...
Saber began to physically fall. Her ass remained up, but her upper half fell slowly, inch by inch. A few minutes ago, her head and wrists were, more or less, at the same height, but now Saber felt herself lowering, her hands still hovering in the air. It was getting harder to keep her body upright.
Seeing Saber's literal fall, Caster grinned and decided to continue to the next step. Pulling out her fingers, she moved in front of Saber and showed her the fingers, slick with her own juices.
“Look, Saber. This is all you. All of this from just a little bit of fondling by me. Why don't you taste it? I bet you'll like it.”
She moved her hand in front of Saber's mouth, and as much as she wanted to resist, her arousal was getting the better of her. Struggling hard, Saber soon opened her mouth and stuck out her tongue, allowing Caster to paint her mouth with her own juices. A part of Saber's mind screamed to bite down, but she instinctively wrapped her lips around them and sucked it down. Saber was shocked she didn't hate the taste. The fact that it was her own arousal just made her even hotter and she moaned around the fingers. Without thinking, she began to suck Caster's fingers, eager for more, which only made Caster smile. When Caster removed her fingers, Saber realized what she did and glared at her captor.
“Oh my, if looks could kill!” Caster said, “But we both know it's just a sham. And I'm going to show you why.”
A look of terror came across Saber's face. She was already struggling, but when Caster went back to Saber's backside, she knew she was in big trouble. Saber feared Caster putting her fingers back in her, but then she felt Caster's tongue and her body exploded in pleasure.
“Ahahaha! I've only just started and you've already cum! Oh, you will be a fantastic toy, Saber!”
Caster resumed licking Saber's pussy, savoring the taste of her arousal. She felt the bound woman sink further to the ground and was overjoyed. Swirling her tongue around, Caster massaged Saber's slit with her tongue, making sure to pay special attention to her engorged clitoris. Every time she did, Saber yelped, so the sorceress happily continued the assault. Saber's pussy was like a leaky faucet now, greatly pleasing Caster. Now that she knew what Saber felt like crossing the edge, she made sure to keep her just before then, denying Saber a second orgasm.
Saber's mental fortitude was in shambles at the moment. She felt her body sink further, both mentally and physically. Her legs fell to her knees, with her head only an inch or two above the ground, held up by the magic circle binding her wrists in the air. Caster's tongue was destroying her body, building a massive flood of pleasure, but then stopping and letting her calm down before resuming. Caster kept Saber on this cycle for what felt like forever and Saber's mind was quickly turning to mush.
This feels so wonderful! Maybe I should submit...
No! I have to believe in Shirou!
But he's taking too long! If he cared, he'd be here!
He will be here to rescue me!
But do you really think he can make you feel this good?
A fierce mental war was raging in Saber's mind, and it was humiliating to admit the devil side was winning. A part of her knew this was part of Caster's spell, making her doubt herself, but at this point that didn't matter. The urge to submit was growing by the second, and being constantly denied another orgasm was ruining her resolve.
Caster lapped up more of Saber's juices and knew she was teetering on the edge. She just needed one last push. Standing up, she made her robe disappear, leaving the woman naked except for her crotch, which had a purple dildo attached to a harness. The modern world had such wonderful inventions.
“Mmm, Saber. I think it's time we finish this and fully make you mine. I'm going to erase that boy from your mind forever.”
Saber, already struggling to remain sane as-is, feared what Caster meant, then panicked when she felt the tip of the dildo at her lips. She turned her head, looking up at her ass being gripped by Caster, who had a large dildo attached to her hips. Eyes going wide again, Saber attempted to break free once again, but there was no escape. Especially once Caster slammed into her.
The temple was filled with Saber's screams as she was properly invaded for the very first time.
“Oh? Could it be that the mighty King Arthur was a virgin? Oh my, that's so wonderful! I'm glad to be your first!”
Saber could only grit her teeth. As King Arthur, she had learned to push aside her body's needs for the good of the kingdom. In order to keep up the illusion of being a man, Merlin cast a spell that would allow her to impregnate “his” wife Guinevere, but Morgan interfered and stole the sperm. Outside of that, Saber had no sexual experience, so she was still a virgin. Well, up until now.
Caster paused, allowing Saber to get used to the dildo inside her, while also savoring the feeling of the walls around it. While the dildo wasn't an actual penis, Caster could activate a spell that let her experience what it feels like, and she groaned in pleasure.
No wonder men are so horny all the time.
Once she felt enough time had passed, Caster pulled back and began to pump her captive, slamming the fake cock as far as she could go.
At this point, Saber was almost completely on the floor. If not for Caster holding her hips up, she would be. Every time Caster thrust her dildo in, another part of Saber's internal wall cracked. She tried to hold the tide back, but deep down, she knew that, if they weren't interrupted in the next few minutes, that she would fall and truly become Caster's. It was inevitable at this point, but all Saber could do was hold out as long as possible and pray for a miracle.
Caster continued to pound her helpless captive, delighted to see her literally falling inch by inch with every thrust. Pleasure raced through her own body, making her pump harder and faster, and Saber to crumple even more. She felt the knight's cunt clench around her dildo and laughed. Caster knew it was only a matter of time until Saber was done, her own body was betraying her.
“How does my cock feel, Saber? Do you really think that boy could compare to me? Drown yourself in your lust for me and fall! Become mine!”
Saber was visibly panting at this point. Moans flowed freely from her mouth. Caster's cock hit her in all the best places. It felt so wonderful, so amazing, that she wanted to give in. Badly. Her body was screaming for it. Even her mind was screaming for it.
You have to give in! She's too strong!
But Shirou...
Who cares about him? He could never make you feel this good!
Shirou...
Doesn't matter, Caster is our Master now!
No! Our Master is Shirou!
Your Master is Caster!
Our Master is... Shirou!
It's Caster!
No! It's... it's... it's...
Caster!
CASTER!!!
Saber screamed at the top of her lungs as a massive orgasm crashed through her body, searing her very soul. Caster's magic broke through one of the cracks and immediately exploded through, destroying her mental defenses in an instant. Saber cried out as her mind was overwhelmed by magic, re-writing her memories. All of her love, her affection, and her duty towards Shirou and Rin were being erased, replaced by images of Caster. She was completely helpless now, unable to fight the inevitable. Caster went from an enemy to someone who deserves worship. Saber's own goal of gaining the Holy Grail, to prevent Camelot's collapse, vanished into the ether. Her goal was now to win the Grail for her Master, the one who encompassed her life completely now.
Caster had removed the dildo and dissolved it and the harness back to the ether, a satisfied smile on her face. She watched as her magic circle glowed brightly, engulfing Saber in its magical energies. She finally had one of the most powerful Servants completely under her control. Hercules, Lancer, and Archer would soon fall before her, and she would obtain the Holy Grail.
After a few minutes, the magic circle dimmed, then disappeared, along with the magic holding Saber's wrists in the air. The still nude Caster put her right hand on her hip and smirked.
“On your knees, Saber. Swear your loyalty.”
The prone king shivered as she came back to the real world. Hearing the voice, she struggled to her knees, not caring that her dress was now stained with dirt and her own arousal. Turning around, Saber sat back on her knees and bowed her head.
“I, Saber, swear my loyalty to you, Caster. I exist to be your weapon and tool. Use me in whatever way you see fit.”
“Good, Saber. And what about Shirou?”
Saber raised her head, a look of confusion on her face.
“I vaguely know who that is, but the details are unclear. Who is he?”
Caster grinned.
“He is someone who is my enemy. I'm sure he'll be here at some point to try and kill me.”
“Then I will have to kill him first. I will not allow harm to come to you, Master!”
A massive, evil grin spread across Caster's face as she started laughing. Saber was confused again, not really understanding why her remark was funny, but went along with it.
“That is wonderful news to hear Saber. Now, while we wait for him, why don't you show your Master just how eager you are to worship?”
Licking her lips, Saber eagerly nodded and crawled forward, soon diving her head into her Master's exquisite snatch. It tasted wonderfully, though because of Saber's inexperience in sexual matters, she didn't really understand what she was doing. Hopefully her Master would forgive her.
Caster moaned loudly, arousal flooding her body. Granted, Saber's tongue was clumsy at best, but for now, she would be able to ride off the joy of having conquered the former king and made her a slave completely under her power. She couldn't wait to see Shirou's face when they met again.
Of course, he wouldn't be alone. That pesky Rin girl was sure to tag along, bringing her Archer with her.
Caster chuckled. If she played things right, she'd get even stronger while acquiring some new toys.
After all, she already has two Servants, why not one more?