The Tower of Passion

Fiona woke up the next morning in a groaning, sore pile of limbs. 
"This was reckless, but entertaining" A mildly amused stern voice said from somewhere nearby. "Certainly the centaurs have an idea of our party's proclivities, however, I do believe the four of you need to get up now. We will be setting off before long."

Fiona dislodged a green arm from her one tit and a small muscular one from another. A fluffy tail was wrapped around her cock, and through several minutes of effort, the party was back up and standing, barely dressed, entirely disheveled, fully disentangled. They had gotten a bit overeager - after Liddy had her go, Fiona was ready again, Ash brought out her lube and it was all a messy memory of pleasure and fun since then.

And now she was sore. And stiff. Qae, who had absolutely been watching them the entire night, had at the very least cooked breakfast for them.

"I spoke with Penthi this morning - they will bring us to their main camp, which is were apparently their current conflict with the Earthen started. At least one particular Earthen." They'd been talking about what they thought they'd have to do to befriend them. The relationship between the Thunderers and the Earthen was always strained - but apparently one earthen had decided to take an important cultural site to the centaur as his home, and they were unhappy. They were also unable to carry weapons on it - but outsiders could. The two factions never came to outright wars, just minor spats and skirmishes regarding the future of the plains. The centaurs wanted to keep it flat, for running and hunting. The earthen wanted to build pits and mounds, maybe even mountains for them to live in. Mostly they stayed out of each others way, and when they didn't, they had a fight.

"How long until we leave?" Fiona asked, her sore legs and ass questioning. 
"An hour, maybe two." Qae said again. The rest of them were still disheveled, hair everywhere, Ash's makeup runny. Fiona didn't mind much, at least she didn't think the centaurs did so. She was fine.
"Right. I need to speak to Penthi." She stated, mostly to herself as she struggled to her feet. They really had gone hard last night.
"Oh? Already - normally you wait until we clear the floor!" Liddy joked, snortlaughing at herself.
"Not for that" Fiona said, blushing again. She had to be more confident, stop that.
"I need to learn to ride better." 

She walked to the centaurs side of camp, trying to pretend a large portion of the beautiful horse women weren't smiling and whispering about her. The camp wasn't big. And, especially for the tall women, was in direct eyesight. She really needed to make better decisions. But, she could also feel herself moisten and stiffen at the thought of the centaurs watching her.

Suppressing that thought for later, she found the blonde captain sat in her human form, cross legged infront of a fire chewing on some grilled vegetable. She had to ask about the forms, but first.

"Uhm, morning Captain Penthi" she started, unsure how to ask her question. 

"Oh! Fiona - you where excellent yesterday, we thoroughly enjoyed you and your friends performance. Great rutting!" The centaur laughed, and the humans cheeks went scarlet red as she stuttered.

"Ah...welll we... uhm. I hope we didn't disturb anyone."

"Nonsense. It was impressive! Have a seat, how can I help?" She patted the ground next to her, and Fiona sat down, the two loin-clothed women looking into the fire for a moment.

"Am I riding with you again today?" She finally asked, and Penthi nodded. 

"Unless you had any complaints - why?"

"Uhmm... could we maybe practice? Before we set off... I'd like to be less scared." She shifted her feet in the dirt, looking down. It had been embarrassing. Everyone else had enjoyed it, and she'd screamed with her eyes shut the entire time. It wasn't her proudest moment. Certainly not impressive.

"Of course! It would be beneficial if you hold on with less strength" Penthi laughed and patted Fiona's bicep. "You are strong. Strong as a thunderer. Almost." She went back to finishing her breakfast, before standing up, powerful human thighs in front of Fiona, loincloth that couldn't be hiding anything other than a pussy right in front of her face.

"Step back a bit, I will swap to my stallion form." She said, as Fiona scooted backward and the tan warrior started her shift. It was rapid but not instant- her legs glowed and warped for a second, her torso shooting upwards. And there she was. Full centaur, with every piece of equipment.

"Stallion form..." Fiona started. "We were uncertain how to refer to your shifting." Fiona said, happy to have the right term now.

Penthi gave a mischievous smirk. "Stallion and Mare forms - we are all both, I thought I saw you being the same?" She stared at Fiona's crotch, the slightly swelling cloth not hiding much. "but in a single form. Challenging."

Before Fiona could ask any more questions, Penthi walked over to a supply bag they had, carried by one of the other centaurs, and came back with a handful of items.

"This is normally used for those injured or unconscious in Mare form, unable to move... but it may help you feel more secure." She placed the items on the ground. A simple saddle, stirrups, and two harnesses, with a strap between them. Right. For the injured, and those unable to support themselves. Still sitting up straight in the saddle in this world, this floor 

Fiona would rather be embarrassed than terrified and nodded her agreement.

"You will have to attach the saddle, don't worry I will help you through it." Fiona took the saddle and placed it exactly as the warrior said, stirrups falling down the sides of the centaur. Adjusting it and positioning it to the thunderer's comfort, Fiona figured this must be much easier than saddling a horse and enjoying the soft brushes against the chestnut fur.

And then she bent below Penthis body to grab the strap from the other side, and she came eye to eye with Penthi's Stallion. It was... enormous. Significantly larger than hers, and hers was ridiculous. She supposed the Mare forms were eight, nine feet tall at least but... this was a true monster, thick and flared horse cock. She'd had similar toys on earth but nothing this size, nothing with that kind of heat emanating from it. Heavy balls hung behind it.

"What you looking at down there?" Penthi joked from above, snapping Fiona out of it as she finished getting the other part of the strap, tightening it to the warrior's specifications, trying to not notice the bemused look on the blonde's face. Wiping the bit of drool from the side of her mouth. Fuck that thing was big.

"Is that attached right?" She asked, ignoring the previous question, stepping back to look at her handiwork. Not looking anywhere else. No sir.

Penthi moved a little, and trotted about in a circle to see how it felt.
"Fits great, now, harness!" She knelt on her forelegs and bent forwards, a very awkward movement, picking up the harness and handing it to Fiona. She knelt fully down as Fiona grabbed the bundle of leather, and as the centaur pointed out which part was for her she stepped into them and tightened it. She had to adjust 

slightly to avoid this comfort, but soon it was fastened around her hips and legs, and she went over to Penthi and sat in the saddle.

"We can't fight with this but it will help you as we travel." The centaur said as the human handed her the other end of the strap, a sturdy-looking belt Fiona helped her wrap around her waist, and a short rope kept the two together. 
"You can still hold on if you want... I don't mind. But you shouldn't need to - hold the saddlehorn, and the strap will keep you safe if you fall. I can stop and lift you up." Fiona felt her body jolt as Penthi stood up.

"Now shall we walk around a little before we have to run with the herd?" She looked back, blue eyes questioning. Fiona nodded. And they were off back into the tall grass, speeding up slightly - nowhere near the speed she had yesterday, but white knuckles were grasping the saddlehorn.
"You managing back there, warrior?" Penthi asked, looking back seeing the queasy human and slowing down slightly.
"Yeah, I... It's just.. Not used to the movement." Fiona started, her hands reaching out to hold the woman's waist instead. Not hard, just... supporting.
"Is that better?" The centaur asked not looking back this time, just moving around.
"Yeah... Is that okay?" 
"Of course - Don't tell anyone, but I dislike riding in mare form as well..." She sped up a little, checking in on Fiona. "I agree the movement is... strange."

Fiona was surprised.
"But you're... That. How?"
"Why would I like it? I can run on my own - Thunderer's only ride if injured or with child. Otherwise, we run ourselves." She sped up a little, Fiona managing to not start screaming yet. It was nice, once she got past the terror. The wind rushed through her hair, the endless ocean of grass in every direction. Thinking about Penthi's answer, it made sense she supposed. Adult humans wouldn't be used to being carried around and it was kind of the same.

She was relaxing. Her hands were not leaving Penthi's waist, but she was relaxed. At least able to enjoy the rush, just a little.
"I get it.. And this is fun." She smiled. It was fun. Riding a beautiful wom - riding a centaur, through endless plains, it felt free. Wonderfully free.

"Can I ask you a question Penthi?" She held the woman's waist a bit tighter as she sped up. "Two actually, I guess."
"Of course - go ahead." She said, the joy clear in her voice. The Thunderer woman absolutely loved running - they were still circling the camp, larger and larger circles now.

"Well, the first one is... How do you decide who's what form? You know... When you... Who's the stallion and the mare?" She was a bit shy, but she was so curious - it was such a weird dynamic, that they could change at will. "And Qae said we are helping you with a cultural site? Some Earthen had taken it as a home."

Penthi looked back as she sped up further, almost getting just too fast for Fiona. The blonde woman smiled.

"The answer to both is the same." The smile turned to a grin.
"The Breeding Run"