Twilight paced the halls of Canterlot Castle nervously. Her day had been non-stop panic and now that she had a moment of calm, it was all really starting to sink in.
Starlight Glimmer's first Friendship lesson.
Her niece being born an alicorn.
Said niece accidentally destroying the Crystal Heart.
Scrambling to find a means of restoring the Heart before the entire Crystal Empire was buried under an unending barrage of ice and snow.
And, oh yes, checking King Sombra's study for any information on the Heart, only to find the tyrant hidden down there, somehow still alive within his dismembered horn and quickly regenerating his body in the Heart's absence.
While her niece's power fluctuation had been dealt with and the Crystal Heart had been restored, arguably the greatest threat remained. Fortunately, the other Princesses were in the Empire as well, meaning there was plenty of magical energy to transport Sombra to the Canterlot dungeons without causing a panic or risking him getting free.
Which lead her to her current location. Celestia said she had a plan, they were just waiting for another pony to arrive. As she passed Celestia's office yet again, Twilight saw a familiar face approaching. "Fluttershy? Are you the one Princess Celestia sent for?"
"Oh! Hello, Twilight," the pegasus greeted her. "Um, yes, the princess asked me to come but she didn't really say why. I suppose it had something to do with you and the other princesses sneaking out of the Empire but I don't want to pry."
"It's King Sombra," Twilight explained. "He's returned... again." Seeing her friend freeze like a rabbit surrounded by timberwolves, Twilight quickly reassured her, "Right now he's helpless, little more than a glowing horn, and under guard in the dungeons, so he's no threat to anyone at the moment. He's healing remarkably fast, however, but luckily Princess Celestia has a plan to deal with him." Gesturing with her hoof for Fluttershy to go first, Twilight used her magic to open the door to the princess' study.
"W-Well, I don't know what I can do, but I'll help any way I can to protect everypony," Fluttershy promised as she took Twilight's invitation.
"...know ponies call Alicorns immortal, but this is ridiculous," Luna was saying to her sister as the pair entered the room. "We could not fell him in battle, he did not age while imprisoned, and now he comes back from having his entire body explode?"
"I know some desire nothing short of execution for him, but that is clearly not an option," Celestia replied. Noticing the younger pair, she went on with a smile, "Fortunately, we have another option. Thank you for coming so quickly, Fluttershy. You and Twilight may be our best hope for dealing with our current situation. Has Twilight told you what has occurred?"
"Yes, your majesty," the pegasus said with a bow, "but I don't know what I could possibly do to help."
"Nothing you haven't before," Celestia said. Seeing the young pair exchange a confused glance, she explained, "Simply put, I want the two of you to reform Sombra."
"WHAT!?" The pair shouted in unison, Twilight's voice louder but Fluttershy's several octaves higher.
Smiling indulgently, Celestia explained further. "Fluttershy, your kind nature and experience with Discord make you the most likely pony to be able to do this successfully. And you, Twilight, were the one who outwitted him to recover the Crystal Heart and one of the two to find and read his journal. I don't think it would be an exaggeration to say that you know him better than any other pony still alive."
"Just don't let him turn that kindness or familiarity against you," Luna cautioned. "Even without his magic, he is a master manipulator. Hopefully, with the two of you working together, you will be able to help each other see through any deceit on his part."
Twilight glanced at Fluttershy, who was once more petrified with terror, before asking, "Are you sure this is the best idea? King Sombra is hardly the same situation as Discord. He was just a lonely prankster with way too much power. Sombra actively enslaved an empire."
"It may sound hard to believe," Celestia replied, "but I have seen what Sombra is capable of without Darkness in his heart. If there is even a chance of turning his power towards protecting Equestrian, it is worth an attempt."
"Just make sure you don't forget that the two are not the same," Luna chided her sister.
"That is not something that will happen," Celestia said firmly.
Twilight glanced between the two, feeling there was something she was not being told, perhaps even a full four-chapter story arc, but Celestia's tone made it clear that the subject was closed. "Very well, your highness. We won't let you down!" Twilight promised. "Right, Fluttershy?"
"Y-Yeah..." her friend replied weakly, obviously still considering all the horrible things that could go wrong and cause them to let Celestia down.
The first thing Sombra became aware of was the sound of a heavy door being dragged open. Then, the quiet yet echoing sound of hoofsteps came to a halt directly in front of him.
“Um... H-hi, Sombra.” It was a quiet, breathy voice which presumably belonged to a mare, and it was dripping with fear. “I don't know i-if you can hear m-me right now, but my name is Fluttershy.”
"I doubt he's conscious yet. He was nothing but a horn this morning." A different voice, firmer and more confident than the other, sounding likely that it too belonged to a mare. Where the other was filled with fear, this one held curiosity as it went on. "Then again, I didn't expect him to heal even this much, yet."
"Oh, r-right. W-well, if he can, um, hear us, an introduction couldn't h-hurt, right?" The voice named 'Fluttershy' suggested.
"I guess not," the other voice conceded. "I still doubt you can hear me, but if you can, my name is Twilight Sparkle."
'So, I was correct on my assumption of unconsciousness,' Sombra thought. 'What is left to be answered is where in Tartarus I am. I assume a dungeon of some sort, given the deathly quiet ambiance looming around me. After all, it is all too familiar to how my own were kept.' Deciding to see if the pair would give away any more information, the fallen tyrant continued his ploy of feigned unconsciousness.
After a few more moments of silence, the voice that identified itself as 'Sparkle' spoke up once more. "See? Still asleep. Even as fast as he's healing, I doubt he'll wake up before tomorrow. Come on, let's get out of this dungeon so I can contact Cadance. I'll have her send over Sombra's journal so that you can read it, too. Getting to know his past better is sure to help."
"Th-that sounds good," the other voice replied in relief, growing fainter as the sound of hoofsteps began to carry them away.
The voices grew indistinct, before Sombra was plunged into silence once more. "It would seem that they discovered the journal I left..." Sombra pondered aloud. "If so, then why would the Two Sisters even bother to send interrogators? Perhaps they doubt its authenticity. I could hardly fault them for that. If not... then what else could they be planning for me?"
Shifting to a more comfortable position, Sombra settled in to wait. "No matter," he mumbled. "I shall no doubt discover what they have planned on the morrow. For now, I must regain my strength and consider how I can best turn this to my advantage."
In the darkness of a castle at night, a young mare woke from her sleep with a start. "What... what was that?" She asked herself as she pressed a hoof to her head. "Such a strange dream. And yet... I cannot shake the feeling that this is something more..."
Sliding from her bed, her mind was racing as she moved to a nearby desk. "They looked so young... If I use that spell... It's a risk, but I can't shake the feeling that something has already gone wrong..."
She hesitated for a moment, before firming her resolve. "If I'm wrong, I'll just come back before anything changes. But if I'm right... I can't afford not to intervene. After all, Auntie Fluttershy was never supposed to be there."