“Um, what do you mean Princess? I know you mentioned earlier that there was some sort of risk to Princess Luna but you didn’t say you were in danger as well,” said Twilight.

“Indeed there is. Luna, if you agree, I’m going to take Princess Twilight to The Vault,” said Celestia in a way that capitalized the letters.

“She has the maturity, responsibility and dedication for it. Plus it will explain to her why you did not want me to try to take a direct hoof in matters. I say ‘yea’,” answered Luna. She turned to face the youngest alicorn in the room, “Twilight, my sister proposes and I agree, that you are suitable to know of secrets most fell. But we shall not burden you with such knowledge without your own agreement. Are you willing to be among the number that are aware of these things?”

“Princess, when have I ever turned down the chance to learn something new? Of course, I am willing,” answered Twilight.

“Even if someday that knowledge may require you to make a terrible choice for the good of all Equestria?” insisted Luna.

“If it would be for the good of Equestria, I would be up for the task,” said Twilight solemnly.

Again the two sisters shared a silent look. Luna of consideration and acceptance. Celestia’s was one of pride at how far her student had come. “Very well,” said Celestia, “Twilight, walk with me.

Leaving behind the Lunar Princess, Celestia and Twilight left the sitting room and made their way through the castle. Down they went, further and further. Until they began to enter the very bowels of the castle. Finally, they reached a long corridor that lead to an iron door. In front of the door stood a single solar guard, standing at attention. As they walked down the corridor though, Twilight had the feeling of many eyes watching her and she spotted several openings in the walls and ceiling that could easily be used to shoot things through. As they approached the lone visible guard challenged them.

“Is Equestria in danger?” demanded the guard.

“No, Guardian. I am here to show Princess Twilight the Vault. Equestria is safe,” answered Celestia.

“Very good.” said the guard. Who then unlocked the iron door and swung it open. To Twilight’s surprise the door opened to reveal a mirror behind it. Similar to the one Twilight had used to travel to Sunset Shimmer’s world, but different. Where that mirror was bright and reflective, this one was ominous and dark.

“Where does it go?” Twilight asked Celestia.

“To a secret vault that lies somewhere in Equestria. Its location is so secret even I don’t know for certain where it is. Let’s step through and I will explain more on the other side,” said Celestia. Together the two ponies then stepped through the magic mirror. Where Twilight found that they had come out into a long wide corridor. The walls, floor and ceiling were all made of some type of smooth stone. About every twenty to thirty feet was an iron door inscribed with a cutie mark or other inscription. The hallway itself was lit with glowing stones and at each door stood both a solar and a lunar guard.

“Twilight, welcome to the Vault. Behind each of these doors is a weapon, or a tool, or a device, or a stratagem that will destroy with utter finality the most dangerous threats to all of Equestria. If Friendship fails, if Harmony falls, when death is preferable to the alternative, here lie the weapons of last resort,” said Celestia with a voice that could have carved granite.

Twilight looked around and her eyes lit upon the first door. Inscribed upon it were the cutie marks of Luna and Celestia. Gasping in surprise, Twilight spun toward Celestia.

“Yes, Twilight. Luna and I are first on the list of threats. Can you imagine the devastation should either Luna or I turn our minds to destruction?” said Celestia. “Do you remember when you were chasing Starlight Glimmer through alternate worlds?”

“Yes, I do,” answered Twilight, “every world was worse than the last one. Until...” Her voice trailed off. A look of sick horror coming over face as she looked up at Celestia.

“Until you came to a world where everything was dust and ash. A world devoid of all life. A world where I had become Nightmare Star and had burned the world,” Celestia said. “As long as there are beings that can do that there need to be weapons to stop them.”

“Why didn’t you use one of these weapons on Tirek?” asked Twilight.

“We did,” answered Celestia, “You.” Twilight’s eyes widened in shock. “And if Discord hadn’t had his power added to Tirek’s you would have killed Tirek in battle. But we hadn’t updated the plan to account for Discord being loose,” Celestia paused a moment, taking in Twilight’s expression of shock. “If you want to back out, I will think no less of you. We have a Zebrican potion here that will erase your memory of the past ten minutes, so you won’t have to carry the knowledge of what you have seen.”

“No Princess,” said Twilight as she shook off the shock of what she was being told. “I said I could handle this and I can. It’s just a bit of a shock, is all.”

“I had a feeling you would say that, but I had to make the offer. Come, I’m going to show what lies inside the vault for Luna and me,” said Celestia. As the door opened she followed Celestia through, entering a stone room along with the guards who had been been guarding the door.

“Twilight, please stand inside the silver circle opposite mine and let the guards secure you in place,” ordered Celestia moving to stand within her own silver circle set into the floor. Each circle was inscribed with a number of runes and was surrounded by a ring of ring bolts set into the floor. As Twilight moved to obey she could see the two guards begin to chain Celestia in place with multiple restraints.

First, all four hooves had cuffs locked onto them. Each cuff was then chained to four different ring bolts. Then what looked like an overlarge corset was wrapped around Celestia entire barrel, trapping her furled wings beneath it. The corset was secured on Celestia’s underside. Padlocks securing the ends together and chains running from the locks to ring bolts on either side. A padded collar was then locked around her neck and again chains ran off in four directions preventing any movement. Finally, three inhibitor rings were strapped to Celestia’s horn, cutting off all access to magic.

Twilight gulped as the guards finished their task with Celestia and began to move towards her.

“It’s okay, Twilight,” Celestia called, her bonds rattling and clinking as she tested them, “if either of us broke free during the next few minutes it would be an utter disaster. The restraints are for our safety.” Twilight did her best to hold still as the guards secured her in the same manner as her mentor. By the time the guards were done all either alicorn could do was to turn their heads to look at each other.

“You have three minutes once we leave Princess, and the shield is set for a three minute exposure,” said the guard.

“Thank you, that should be plenty of time,” replied Celestia to the guard, “Twilight and I will see you in six minutes or so, then.” The guard left, the sound of locks slamming into place coming from the door. Then, the ratcheting of some sort of mechanism could be heard clicking away through the walls.

“Princess, what is going on? Why are we chained like this and what does any of this have to do with what is going on?” demanded Twilight. She was trying to hold still but could not stop herself from testing her own bonds. There was no give at all. She was inescapably held in a firm metal grasp.

“Twilight, at the end of the war with the Crystal Empire, Luna and I attacked Sombra directly, in his throne room, on his own ground.(1) We were winning the war and we did that anyway. Do you know why?” asked Celestia.

“Not exactly, no. Everyone has always assumed you wanted to bring the war to a quicker end to save more ponies,” answered Twilight after a long pause.

“Only in part. Luna and I attacked because we were afraid. We had learned that Sombra had created a weapon specifically meant to destroy Luna and myself. A weapon that incorporated a portion of our essences. And just like how Side Slip is able to reach into you through your essence in him, so too can Sombra’s weapon reach into us and unmake what we are. We had to strike before he could use it on us.”

“That’s horrible! But what do you mean ‘unmake you’ and you still haven’t explained why we are chained?”

“Sombra did not just want to conquer Canterlot. He wanted Luna and myself as alicorn broodmares. He knew we would rather die than submit, even if he won the war. So his weapon was intended to unmake us as princesses and turn us into willing sexual slaves to his lusts. To not just allow ourselves to be violated but to make us want and crave it.”

“And our chains?” asked Twilight, trying to move her neck back and forth more than the half inch the chains and collar allowed.

“To keep either of us from using the weapon on me while I show you its power. Now brace yourself. The shield is about to come down,” said Celestia.

The ratcheting sound that had been in the background suddenly ended in a large ‘clunk’ and a section of the wall opposite the pair slid down. Revealing a pair of glass cubes bolted to a shelf in the revealed niche. In either cube was a leather bridle. The bridle on the left was dyed white, set with sunstones and the words ‘Conquered Sun’ in gold stitching. The one on the right, midnight blue, set with moonstones and the words ‘Chained Moon’ in silver stitches. Both bridles began to glow with magic auras. Twilight could feel the malevolence coming from the enchanted bridles. Some horrified part of her absently noted that the leather of the bridles was tanned pony hide.

“They’re horrible,” Twilight said in a quiet voice, “they’re beautiful.”

“They had to be, they had to be beautiful so the piece of us in them would feel at home. And they had to be horrible so as to twist and corrupt that self-same piece of Luna and I,” Celestia gasped as the aura of the golden bridle began to wash over her fur.

Celestia moaned and shuddered visibly, “The piece of us in the bridles wants to be whole again so it tries to come to us. But it was corrupted by Sombra to make me into the willing slave of whoever puts it onto me. And,” Celestia paused as another shudder wracked her frame. “At this range it’s power affects me directly. If it wasn’t in the cube it would fly to me under it’s own power and bind me to it. Even now it’s trying to make me walk over to it and put it on. To submit to Sombra, or absent him the closest pony that can use dark magic, as he did.” Celestia sent a smoldering look over to Twilight.

“Celestia, please focus! If the weapon is here why can’t you or Luna go to the Badlands?” Twilight pleaded to her mentor as she saw Celestia’s will crumbling before the corrupting onslaught of Sombran relic.

“The dogs,” Celestia gasped, “The Diamond Dogs were Sombra’s allies. Some of them even after they signed the treaty with us. Sombra almost certainly sent them duplicates of the bridles along with all the other weapons he sent to them. Sombra...was too intelligent not...to have made backups.” Celestia began to tug and pull on her bindings, as her will was washed away in golden light. “Please Twilight, “ Celestia begged, “I can’t resist it anymore, I beg you, take the bridle, take me, make me yours.”

“I -,” Twilight paused as a feeling of warmth began to spread over her. The auras of the bridles had spread to cover the entire room. She suddenly realized she had been so worried about Celestia that she hadn’t considered that the bridle might affect her as well. Twilight decided a moment later that it didn’t matter though. Why shouldn’t she bridle Celestia? She was right there. Chained, helpless and utterly delicious. Celestia’s tail was flagging now, spreading the scent of her glorious arousal around the chamber. All Twilight could think of was how good it would be to plunge her muzzle into that scent. To taste the golden nectar of the golden princess. To conquer the sun.

“Just a moment Celestia, give me a moment to fetch your bridle and then you will be mine,” Twilight almost purred to the writhing alicorn near her. Twilight remembered Pinkie showing her how to slip out of cuffs as part of a magic trick. Just a few twists and she should be able to get a hoof free.

“Oh Goddess, yes! Please Twilight, I want to be yours so badly. Claim me, breed me,” Celestia begged as liquid from her arousal began to run down one leg and she fought even harder against the chains, the collar and the corset. If Celestia had been able to generate even a little momentum things might have been different. But the slack needed simply wasn’t there. Which drove the alabaster alicorn into an even greater frenzy that had nowhere to go.

“There!” exclaimed Twilight, as she slipped a fore hoof free from a cuff. Moving quickly, she reached up and worked the inhibitor rings off her horn. The solar princess would be hers. None would claim Celestia before her faithful student. She had earned the right to possess Celestia in trial after trial. Regaining her magic, Twilight created a force dome close around her, which severed the chains securing her in place. The cuffs, collar and corset remained locked onto her but without securing chains they could do nothing from stopping Twilight from achieving her destiny of becoming Celestia’s mistress.

Nothing could stop Twilight now, except the fail-safe. Rigged to activate if the bonds securing either pony were severed or broken, the silver rune ring around Twilight erupted and encased her in a dome of magic, trapping her in place.

“NOOoooooo”, she howled, beating at the dome with her hooves. When it failed to give way she began to blast the dome with bolt after bolt of magic. She was still blasting at it thirty seconds later when the section of wall began to slide back up again. Ten more seconds and the section of wall was back in place.

And with the shield back in place the corrupting influence of the bridles was suddenly cut off. Twilight shook her head, as she began to clear her mind of the dark influence. All lust and desire for Celestia was suddenly cut off replaced by a deep embarrassment. Looking around through the dome she could see Celestia still shuddering but slowly bringing herself back under control.

“Don’t feel embarrassed Twilight,” said Celestia in a much steadier voice as she steadily took deep, cleansing breaths. “You’ve felt Sombra’s magic before. You know how powerful and how corrupting it is. Your reaction was absolutely what it should have been.” Celestia paused again for a few breaths, “Besides, if it came down to the destruction of Equestria on one hoof or my becoming your slavemare on the other, I know that you would take good care of me at least.”

A few seconds later and Twilight could hear the door unlocking as the guards came in. The guards took in the scene in the room. One of them began to towel down Celestia immediately. His nostrils flared at the scent of arousal in the room but otherwise he didn’t react at all to her state. As for Twilight, the other guard looked at her and asked her how she had freed herself. After she had explained how she had slipped one of the cuffs he nodded and triggered the release for the dome, freeing Twilight. Twilight got the feeling that the manner in which she answered had been as important as the words she spoke. He then proceeded to remove the remains of Twilight’s restraints from her.

A couple of minutes later Celestia was completely freed as well and was once again fully herself. As the alicorns began to leave Celestia thanked the guards for their service and their professionalism. Turning to Twilight as they began to walk back toward the entrance Celestia said, “As you saw you can’t protect yourself from a part of yourself. It’s what makes those bridles so dangerous to Luna and myself. It’s also why you need to careful around Side Slip. He has part of you inside him. Deliberately or not, he might influence it and alter your perceptions of and for him. It likely won’t happen but you need to be aware of the possibility. Now, did you have any questions?”

“Yes, Princess I do have two questions,” Twilight asked. “What are we going to do to help Rarity now and is there a vault here with my cutie mark on it?”

Very late that evening
The Dreamscape

Rarity felt that she had walking for hours through the featureless darkness. Up ahead, she spotted a light, so she headed towards it. As she drew near she could see a table, complete with a pair of comfy looking chairs and a tea set with steam coming from the tea pot. Near the table, just inside the circle of light, Rarity could just see what appeared to be a steel cage. It’s door hung open and empty chains and shackles hung from its bars. Sitting on one of the chairs by the table was a pony shaped form that wore a cloaked hood.

“May I have a seat?” Rarity asked as she approached the table. The figure silently gestured to the chair opposite and Rarity sat down.

“Do you mind if I have a cup of tea?”, she asked the hooded figure.

“Not at all,” said the pony under the hood in a familiar sounding voice, “in fact, let me pour that for you.” The pony poured tea for Rarity and as the tea was slid across the table the pony passing the tea pulled back the hood she wore revealing, a twin to Rarity herself! Or nearly so. The mare across from Rarity had her face and features but the other pony had her mane woven into a tight braid and she wore a bridle that lacked buckles to allow its removal.

“For lack of another name, call me Valiente. And we need to talk.”

Author's Note

(1) Fall of the Crystal Empire by SFS Animation. I highly recommend watching it if you haven't already.

So, this is the third part of the mega chapter I wrote over the last half of August and decided to break into smaller parts. This part is about as close to straight up clop as I want to get in this story but I felt it necessary to show the worst case scenarios that are faced. I knew this chapter was coming right from the beginning and its why I tagged the story 'mature' in the first place.

Chapter 7 will bring the focus back to Rarity and will be delayed a bit as it is back-to-school time for my own little ponies. All the best to you and yours.