//------------------------------//
// Explanations 
// Story: Twilight : Bleach 
// by ilbgar 
//------------------------------//

	...Or she could run off to take care of the impostor and leave Cadance here in the capable hooves of Celestia and Luna. Yep, pull an Ichigo and run off to deal with the bad guy by herself. What others thought of her be damned.
She was about to teleport away to do just that, when a powerful anti-teleportation ward slammed into place. She could break through it easily, or simply Flash-step past the sisters and out of range of the ward, but they were clearly desperate to keep her from leaving, as the ward was somewhat hastily constructed. Besides, tearing apart a powerful ward would only cause them to get more paranoid.

*** Celestia's POV ***

"Twilight-" Celestia began. She and Luna were both confused and worried about Twilight. That white doppleganger of her with red eyes had radiated a level of malevolence she'd experienced only rarely. Most of the things that had similar presences were in Tartarus, the rest were either destroyed at some point, or sealed elsewhere.
The power it had wielded was also considerable, it broken the powerful wards and enchantments around the vault holding the elements of harmony with ease, either with a delicate dis-assembly, or through sheer overwhelming force.
One of the wards had had a built-in sub-directive to warn them if it was ever broken down. It had taken them only the better part of a minute to get there, but already nearly every single spell had been broken.
The doppleganger had responded to what they'd said in ways that raised more questions than they answered.
"Oh, no you don't, get back out here dammit!" Twilight said, cutting her mentor off as she made a strange white mask with orange accents that looked like cuts that radiated that same malevolence as Twilight's doppleganger out of the dark energy it had just disintegrated into, she hesitated to call something so foul magic. The curse alone was shocking. Twilight never cursed like that. Ever. She would only curse if thoroughly upset by something, and even then, only lightly. To use a stronger curse was simply unthinkable. It was completely out of character for her.
"I asked you to bring me the Elements, not bring these two along. Don't pretend you couldn't have outrun them if you wanted to!" Twilight accused her double.
The doppleganger smirked. "Well, you never said I couldn't bring them along. Besides, this is payback for sending me to get these things" The doppleganger pointed to the box containing the Elements of Harmony. "when you knew that I'd find it annoying." She was clearly enjoying getting a rise from her technicolor counterpart.
"As... entertaining as this is, we need to-" Luna was cut off by both versions of Twilight yelling.
"Not now!" though the monochrome version yelled it quite a bit louder than her more colorful twin.
Twilight immediately looked sheepish, while the doppleganger was utterly unapologetic.
"Anyway, long story short, I was sent to a parallel world by an impostor of Cadance. The one on the floor, unconscious, is the real one." Twilight said, deciding to try the direct route. It worked more often than not.
"So, that's where... she came from?" Celestia asked, nodding her head towards the doppleganger.
"I'm what's called an Inner Hollow. When someone undergoes Hollowfication, but manages to fight it off, they end up with one of us. A manifestation of their darkest, basest instincts, lacking a heart to balance them out." The white doppleganger explained, not at all concerned with the effect her words would have.
"How is it you aren't struggling with each other for dominance?" Luna asked, handling the news that Twilight essentially had the manifestation of all her negativity in the room rather well.
"Oh, we did at first, she kept trying to take over. Eventually, I got some help from a few people with experience dealing with their Inner Hollows. I managed to defeat her and establish dominance. After that, I could call on her power for short periods of time. Her power appears as the mask you saw, and Hollowfication immediately doubles every aspect of fighting ability. Speed, strength, endurance, energy reserves, maximum amount of energy you can use at once, etc." Twilight answered.
"Short? You got it to 15 seconds before fighting Grimmjow that second time. Better than Ichigo's 13 seconds though." the Hollow said.
"Who are you talking about?" Celestia asked.
"I'll be happy to introduce you once this mess is cleared up. For now, we should take care of the impostor-" Twilight found herself bound by a sealing spell. The impostor had entered the room, and seen Twilight, and so cast a spell to restrain Twilight out of some reflex.
"Well, that's confirmation of Twilight's story if there ever was such a thing." Celestia said, while turning to the impostor.
"This isn't going to be enough to stop me for any significant period of time." Twilight said, before shattering the spell with little more than a prodding by her magic.
That surprised everyone in the room besides Twilight and her Hollow. For her to be able to do so implied that she totally outmatched the impostor in terms of magical power to a degree that bordered on hilarious.
"How are you even here?" the impostor asked, having noticed the real Cadance on the floor and knowing the jig was up.
"I got some help from a crazy scientist." Twilight said.
"You want me to take this one Queen?" her Hollow asked, a note of eagerness clear in it's voice.
Twilight thought it over. "Just don't kill her." she said.
"Kill me? I thought you ponies were a peaceful lot, who are you anyway?" the changeling asked as she revealed her true form.
The Hollow smirked. "So you want to know who I am?" it asked, the malevolence it released at all times spiking. "I have... no name!" it cackled madly before launching itself with terrifying speed at the changeling, who was the size of and looked like a twisted version of Celestia.
The changeling raised a shield, but the shield succeeded only in keeping her from dieing from the first strike, which was accompanied by a wave of black energy that destroyed the shield and dented the cement behind the changeling.
"Well, then let me introduce myself at least. I am Chrysalis, and I must admit I'm impressed at your power. Considering how long I've had to feed, it says quite a lot that you were able to destroy my shield with a single attack. Still, an overpowered beam attack isn't very unique." the changeling said. This prompted laughter from the Hollow, and chuckling from Twilight. "I fail to see what's so funny." Chrysalis said, somewhat annoyed.
"That was just the force behind this blade of mine, let me show you a real attack." the Hollow said, before dark energy flared in a pillar around her. "Getsuga... Tenshou!" the Hollow cried, sending a wave of black at the changeling. It missed and hit the wall, removing everything above that and leaving the cement faintly glowing dark purple. The crescent of black energy continued on, and smashed into the shield around the city, causing cracks, before finally destroying it and continuing into a mountain, which it sliced right through. It kept going, slicing or smashing through everything in it's path, before disappearing on the horizon.
The changeling stared at the white thing in front of her. That... that was impossible. Nothing could have that kind of power. It was insane. "If you think that's impressive, you should see my full power, this is only a tenth, and Queen there has the same amount as I do. Now imagine having to fight against that." the Hollow said, having somehow gotten next to Chrysalis in an instant.
"Oh, and moving that fast was a technique, but that's how fast I can go fully released. Also, I missed you on purpose just now, it wouldn't do to kill you without a fight, that wouldn't be any fun at all." the Hollow's grin was nearing demonic.
Celestia and Luna stared open-mouthed as the full implications of this hit them. Twilight had the kind of power that made the elements of harmony look like trinkets with her power at one-tenth strength. Ten times that much was on a level that reduced them to insects she could step on at any time if she so chose. With the apparent loyalty of an entity of equal power... the very concept was terrifying. She could make the world her playground, and there wasn't a force in existence that could stop her. She might be a good pony, but absolute power corrupts absolutely.
"I've got about ten percent on Ichigo in terms of power. His Hollow's gap compared to mine is the same. We spar regularly." Twilight said.
There was somebody on her level?! While shocking, it was also a relief. That meant that there was someone who stood a chance against her, so she wasn't likely to go mad with power.
"So, care to surrender?" Twilight asked cheerfully.
"Please say no, nobody wants to fight us except Ichigo, Ichigo's Hollow, Grimmjow, and Kenpachi. Three of them are definitely crazy, the other one is debatably so." she cocked her head to one side. "Then again, I guess I'm not one talk." she chuckled, her scythe blade suddenly at the changeling's neck.
"Alright! Alright! I clearly have no chance of victory here!" Chrysalis said.
"Aw, and here I was hoping for a fight." the Hollow sighed in disappointment before lowering her scythe.
"Well, shall we get the real Cadance some medical attention, or what?" Twilight asked, turning to the princesses.
Celestia and Luna started, then Celestia nodded. "Yes, of course, we'll have to inform your brother and your friends of these events of course." she said.
"Whatever, but don't even think about trying to use the elements to get rid of me. Queen'll never go along with it and..." she reached in the box, took out the Element of Magic, and pulled on it, a bleached white version of it coming away. "I don't think it would work on me anyway." the Hollow was wearing a huge smirk. She put the tiara on. "Do you think this looks silly on me?" she asked slightly mockingly, posing.
To their credit, neither Celestia nor Luna lost their composure this time. Though the white version of the Element of Magic was practically oozing dark magic, which was probably a whole new level of disturbing for them.
"Ahem, yes, but first we must deal with this one." Luna said.
"Well, we could throw a few power limiters on her and then chuck her into the dungeons until we can get Cadance and Shining Armor fixed up enough to let them decide." Twilight suggested.

*** A Surprisingly Short Time Later ***

After a couple hours, everything was set. The girls were all assembled, along with Spike and her parents, and the princesses. Shining Armor and Cadance were present as well. Shining Armor was actually surprisingly easy to fix since Chrysalis was currently under the (correct) impression that she'd be in very real danger of dying if he was permanently damaged in some way and was giving them her full cooperation. Cadance woke up shortly before him, thanks to a little more healing magic. The reason they were assembled was so Twilight could explain about her new abilities and... friend.
Twilight was also promising to introduce them to some friends she made along the way. They were all eager, for various reasons, ranging from concern to curiosity. They entered the room Twilight had commandeered for the occasion, and discovered a hole in the fabric of reality. They were left in varying degrees of shock as Twilight greeted them cheerfully.
"Well, this is how I got back to Equestria, and it's how we'll go visit Karakura Town." Twilight said. After some coaxing, she got everyone to go through.
They came out, and were surprised to discover that they'd changed. First off, they weren't ponies anymore, second, they were wearing clothes now. Thirdly, the moment they got there, a strange creature with a white mask and a sort of heaviness to it's presence rushed them, only to be skewered by Twilight. It dissolved into nothingness, and the heavy presence just disappeared.
"Huh, a Hollow already? How strange." she said, as if nothing odd had just happened.
Rainbow Dash summarized their thoughts. "What the heck!?" she cried.