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A/N: Pushing the teen rating here. But there's nothing graphic, so it should be A-Okay!
Celestia felt a wad of mud slap against her face, and blinked.
"Falling asleep on the job again, Tia?" Leaning on the castle's door frame, hands aglow with summoning magic and ankle deep in mud stood the hero of Equestria and the most recent of its princesses. She wore a confident smile, eyes dancing with excitement and anticipation, and her hair was a messy mane where it was usually a firmly combed set of bangs. This, of course, was not the part that Celestia was focused on, however. That would have been the part where she was clad only in a skinny, flimsy and revealing bikini, liquid earth splashed around her waist, calves and back.
"...Twilight? What exactly..." Celestia's response came out far more halting and confused than she would have liked. In two seconds the entire framework of her day had been inverted by the woman she loved in a way that seemed completely out of character for her. She vowed to herself to get to the bottom of it. She decided, upon noticing that her eyes traveled from Twilight's smooth, flat stomach down towards her slender hips and, well, bottom, that she had selected a very poor word choice.
"This is the fifth time some villain of Equestria has left you completely powerless while I've come to save the day. Luna thinks you're losing your touch. I think you just like the thought of being rescued. But whatever the case, the three of us have decided that we need to see if you've still got it. That fight with Chrysalis, I mean, wow, that was bad."
Celestia bristled with anger, the blush from her ogling replaced with a burn in her cheeks that was of a very different nature. I suppose I should have known that Twilight found the courage to surprise me like this through consultation. Luna will be the death of me yet, I suppose. "And what is that supposed to mean, my faithful ex-student?"
"Quite simply, we, well, mostly Cadance and Luna, think you need some practice in fighting to make sure that the girls and I aren't always the ones saving the day. I decided that you and I could have a little fun while we tried that." Twilight slapped her thigh with a glob of mud for emphasis, spreading the slick of brown across the entire throne room's floor. Enchanted, the mud rushed up the stairs to her chair as quickly as it had run towards the walls. Celestia lifted her feet up in order to avoid staining her slippers. Twilight gave a devious smirk. "Here, let me get that for you."
Celestia felt the electric tingle of a dissipation spell surround her, but her counterspell found nothing but thin air by the time she had prepared it. The tingling was replaced by the sensation of cold, and it was then that she realized that Twilight--meek, timid, hero-worshipping Twilight--had just stripped her to her skivvies. Celestia crossed her legs and raised her hands across her bra instinctively, a flush coming over her. What has gotten into her?
"Twilight, what is going on here?"
"I've already said what's going on here. I'm challenging you to a friendly spar to see if you and I need to practice defense against threats to Equestria together." Twilight stretched her bikini top straps, making sure they were ready for the confrontation ahead before letting them snap back into place. Celestia's eyes followed them on their journey against her will, noticing the shadowed tease of what they concealed as the cups of the top lifted ever so slightly to show bare, rounded flesh not touched by her sun’s rays. "I'm worried that I won't be able to defend you all the time, and I thought that the best way to see if you can defend yourself would be to come at you with everything I've got. Then I realized that that might lead to a fight." Twilight began to march towards Celestia, making sure her slender, knobbed hips swayed in time with her walk. Celestia felt a rush of blood at the sight of her gleaming skin dancing back and forth against the thin line of cloth that concealed what little of her girlfriend's body she had yet to see.
"So I decided that it would make more sense to make it a game. And then I realized that Luna and Cadance would want to join in unless I made it a game they would be absolutely repelled by. Namely, watching their sisters fool around with each other. And...I may have wanted a chance to, eh heh, play around a little myself."
Celestia felt her panties lift, then smack down against her bare bottom with a slap that rang around the throne room. "Twilight! You could have just, you know, asked!"
Twilight gave a smirk, at last reaching the steps to the throne and pulling herself up the stairs towards Celestia. "Discord and Tirek don't just ask to take over Equestria. And besides, you would have said no, I'm sure. Now come on. We took a risk when we first hooked up, and we’re going to take a risk now.” Twilight’s hands glided easily across the air, parting the mud into a circle with a line dividing it into two equal sections. “And this time I’m the one who’s calling the shots here.” With another flick, Twilight knocked the crown off Celestia’s head, tweaking it on its journey with pulses of magic so that it landed squarely on her own scalp when it was done. A set of wards shimmered through the air around Twilight’s head.
“The game is simple,” She said with that same devilish smirk. “You get your crown back, and I’ll tell Cadance and Luna they don’t need to worry about you getting soft and…” She looked down at Celestia’s pudgy, nude stomach. “...Flabby. I win, and you’ll be learning from me for the next few months, in the same way.”
Celestia mulled over this against her omnipresent blush. “That sounds fair to m--”
“And I get to choose what on your schedule I interrupt to do this, barring international crises.”
Celestia’s eyes narrowed. “What’s the time limit?”
“Two minutes. This is our arena.”
Celestia responded to this by grabbing Twilight by the ankle, flinging her off her feet with a single grip of her pinkie finger. To her disappointment, the crown did not fly off Twilight’s head. Instead, Twilight simply created a dimension door directly behind herself, letting the momentum of Celestia’s magic swing her through it. Celestia felt a foot at her bottom at the same time that she was launched off the throne room and into the mud at the base of the chair below. With a squelch, she landed face first in the goo, her hair floating around her like an oil slick.
Twilight landed beside her, a different spell ready in each hand. “You can always give up now, you know.” Celestia brushed some hair out of her face, pulling herself out of the mud with a squelch.
“Catching me off guard doesn’t mean beating me.” The mud around Twilight’s ankles became as hard as ice, sticking her fast to the ground. Twilight fired off her first spell, which opened in a flash of green light and threw her former mentor backwards. The resulting summon drenched Celestia in a particularly unpleasant green slime and blasted her against a wall, sticking her to it as if it were flypaper.
“You should have gone for the hands.” Twilight’s smile was rivalling Discord’s in deviousness. Celestia only groaned, twisting her wrist in an attempt to free herself. Next Twilight covered her in octopi, then levitated her into a giant tea pot. “I’m not seeing any attempt at resistance. Does that mean you give up?” Twilight shook the tea pot, then dumped it onto an equally massive cake. Spells of all sort penetrated the cake. This one turned Celestia into a monkey. That one made her hair spank her like a whip and wrap around her eyes and arms. Another tickled her across every surface of her body, making her writhe and laugh within the sinking mound of pastry. More and more ignoble fates befell her as the frosting collapsed, leaving her at last lying in a giant puddle of liquid dirt and sugar.
Celestia, fully drenched in all manner of slime, goo and fluid, clawed her way out of the remains of the cake and wiped her eyes. “I think it solidifies my stance on the matter.” It was here that she twisted her arm once again, and the mud that had been creeping up Twilight’s legs fastened around the cloth of her bikini bottom. With a yank and a smirk, Celestia pantsed her lover.
Twilight’s eyes widened, and her hands flew towards her hips without a thought. Celestia, naturally, ensnared them with the mud she had been amassing across the various punishments and humiliations Twilight had thrown at her. Letting the brown sludge harden once more, she walked over to the now mostly naked Twilight and casually placed the crown back on her head.
“I win.”
Twilight, despite her compromising position, smiled. “Nope. Two minutes and forty five seconds. You should have picked a quicker strategy.”
Celestia did a double take. “What?”
“I win. I knew you were going to try something subtle. I just also knew it was going to be hard to do with all the jostling around I gave you. I made it hard for you to focus for a reason. Well, that, and for fun. But mostly to win. If I’d just thrown basic combat spells at you, you would have deflected them and kept your cool. So I broke your focus.” Twilight gave the first open, earnest smile since her entrance. “I know you better than that, Tia.”
Celestia smiled down at Twilight, who was still bent over and surrounded by mud, undressed but victorious.
“So, when do you want to start our lessons?” Smug Twilight was back, and all at once Celestia’s smile took on a much more devious shade itself.
“Oh, whenever somebody deems it best to free you.” Twilight’s smile vanished, replaced by confusion.
“What do you mean by that, Tia?” Celestia turned on her heel, walking away from the mess that was the throne room with a triumphant grin. A mortified Twilight struggled against her bonds, waving her naked bottom high in the air as she fought against the makeshift cuffs. “Wait, Tia! Somebody will have to clean this up! I’m still not dressed! Tia, come back! Tia!”