When one thinks of Canterlot, many things come to mind. It's magnificent libraries, the great School for Gifted Unicorns, or perhaps even it's glittering crown jewel, the Royal Palace. But these are the pleasant places, and as even the most innocent of ponies know, not everywhere is as wonderful to behold as those. For deep within the lower levels of the Royal Palace, there was a place seldom visited, and even less often used. The dungeons. Almost nopony could remember the last time these places were needed, but today, there was one who did.

For along the halls of that place, standing outside and old and heavy wooden door, was the absolute last person anypony expected to find down here. A beacon of light in these dark and dingy chambers, this was a mare that all in Equestria, stallion, mare and foal alike, looked up to. Princess Celestia, the monarch of the sun, and co-ruler of Equestria. She did not want to be here in these low places, but she had to be, for what she was planning was far too important to risk by letting anypony become involved with it.

She took a deep breath before letting out a long sigh, then reached up with a hoof to touch the door. But, before she could, a very familiar voice called out to her.

"Sister?"

Celestia's eyes shot open when she heard those words, and her face became one of both fear and worry. As she slowly turned her head, she saw that she had not been imagining things. For there she was, her younger sister, Princess Luna, ruler of the moon. The younger mare was walking towards her elder sister, her face bearing a look of both confusion and concern. On any other day, Celestia would have been nothing less than happy to see Luna. But today was not like any other day, and she knew that what she planned was not something her sibling would want for her. Even so, she stood firm as Luna came within just a few feet of her before speaking.

"Celestia...what are you doing here? I've been looking for you all day, but nopony had seen you."

The elder Princess looked away from her sister, her expression almost one of shame. To want to deceive her own flesh and blood like this was not something she ever wanted to do, but she felt she had to, if only to avoid causing Luna any concern. With her now discovered, it was clear to Celestia that no amount of explanations on her part would satisfy the younger alicorn, save for the absolute truth. Looking at Luna once more, Celestia steeled herself before speaking.

"I'm sorry I didn't tell you, sister. But...I didn't want you to worry about me."

Luna tilted her head in confusion over that, not quite sure what Celestia was talking about. However, before she could enquire further about that, a sound disturbed the silence between them, a metallic rattling of some sort, coming from the room behind the door Celestia was standing next to. Luna's eyes darted towards it immediately, as did Celestia's, before the former looked to her sister qith a quizzical look. Celestia knew that there was no hiding it any more, and so she raised a hoof ansd placed it upon a sliding section of the door, which was placed at eye level, moving it aside to reveal the room within.

The younger alicorn looked to that opening, then to Celestia, who bore a look of shame upon her face. Luna slowly walked towards the door and began to peer inside. Her eyes widened, either in shock or horror, Celestia could not say. But it was clear that Luna understood what had just happened, as she backed away from the door, turning towards her sister with her eyes still wide.

"Sister...what have you done?"

Celestia hung her head low and stared at the stone floor, but only for a moment, for she too now walked towards the opening and gazed inside, to see the object of Luna's shock. Within the dark and cold chamber was a figure. A stallion bound on all four legs and his neck in heavy iron chains, connecting to the walls and floor. He was a unicorn, dark grey in his fur and jet black in his mane. But his horn was not that of regular unicorns, rather it was curved, and bright red in colour. The stallion's eyes were a fierce green and glowed brightly in the darkness of the cell. On top of everything else, his mouth was covered in a metal muzzle, which was connected to his neck brace with chains like those on his legs.

As the stallion looked up, seeing the sun Princess looking within his cell, he began to stir, railing against his chains as best he could, but unable to break them. As she gazed upon his stallion, so full of anger, Celestia sighed once more.

"Oh...Sombra."

King Sombra. It was a name known far and wide as one of the most notorious tyrants in Equestrian history. Everypony knew the tale, that of a unicorn whose heart was as black as coal, emerging to conquer and enslave the ponies of the Crystal Empire. Through Celestia and Luna's efforts, the fiend was banished for a thousand years, only to be vanquished entirely when Twilight Sparkle and her friends ventured to the Empire once it re-emerged from Sombra's curse. But, although everypony knew that story, what they did not know was that this Sombra was not the one they'd heard of.

No, this was not the stallion who conquered the Crystal Empire and fought Celestia and Luna. This was a wise and peaceful king, who had ruled his subjects fairly. For this Sombra was, after all, not of their world. Rather, he was from an alternate version of Equestria, one that Celestia, Luna and their friends had been to by way of a magic mirror. There, so many things were different, the most notable of which was the fact that the great evil which plagued that world was not Sombra, as most would assume, but rather that world's version of the two sisters themselves.

However, though great effort, those Princesses had been freed of the evil that held sway over their hearts, but at a terrible cost. For evil like that could not be destroyed, merely moved to another host. And that host was none other than Sombra, who sacrificed himself to free the two Princesses and save that world. That darkness now remained within him, twisting his thoughts and his very soul, and it was for that reason that the once kind King now glared with hate at his captor, all while Celestia looked one with sadness in her eyes.

Luna meanwhile was looking at her sister with confusion on her face.

"Celestia...how? The mirror was shattered. There was no..."

But then she stopped and, for a brief moment, pondered on her words. In just a few moments, a look of understanding dawned on her, and she looked Celestia straight in the eyes.

"The shard. You..."

Celestia nodded, confirming Luna's suspicions. When the magic mirror connecting the two worlds was broken, Celestia kept one of it's few remaining pieces. Although initially kept out of sentiment, it was only recently that she considered using it for another purpose, which she now explained to her sister.

"It took a lot out of me, but yes. I used that remaining piece to allow travel between the two worlds. A one-way trip, and of just one pony."

The elder Princess turned away from Luna and back towards the door.

"Him."

Luna shook her head, still not believing that her sister had done this.

"But...why? Why do this to yourself?"

Celestia looked at the ground, her expression one of melancholy. She knew her sister cared for her well-being, but even so, she felt that she had to do this. It may indeed cause her pain, as Luna feared, but Celestia knew in her heart that she'd feel even more pain if she merely did nothing, which was a fact she was more than willing to voice to Luna.

"I couldn't do it! I couldn't just leave him there!"

Luna opened her mouth to speak, perhaps to try and dissuade Celestia from this path she knew she was going to walk, but she stopped herself. She knew her sister well enough to know that once she set her mind to something, she wasn't going to stop. If this were anypony else, she would have called it folly that she would attempt something like this. But this was no ordinary pony, and this Sombra was far more than just an ally to Celestia. He was a stallion that had grown close to her, far more than the sun Princess would have ever thought possible. It was a shock, to her and all who had heard it, but the truth was right there.

She had fallen in love with him.

The younger alicorn knew that it had broken her sister's heart to leave Sombra in that other world, knowing he'd fallen prey to the same evil corruption that had claimed the Sombra of their own world. In a brief moment, Luna pondered whether she too would take such actions for love, had their positions been reversed. A silent glance between the two sisters told them everything they needed to know. Celestia understood that Luna still had her reservations about this, but the elder sister nevertheless put on a smile, and raised a hoof to Luna's shoulder.

"Don't worry, little sister...I know what I'm doing."

Luna looked at her sister's eyes, trying to see if there was any doubt there. But there was none. At the very least, this meant that Celestia had faith in what she was doing, and though Luna still had her own doubts, she was at least willing to allow Celestia to pursue this matter of her own accord. Letting out a sigh, Luna nodded, and Celestia smiled once more. That smile faded however when she turned her attention back to the door. It was unlikely that Luna was going to leave her, now that she knew Sombra was here, so, she walked towards the door regardless, opened it, and walked inside, closing the door behind so Luna could not hear what now transpired within.

And so, here they were. Two ponies who not long ago had been inseparable from one another, now divided in a way that none could have foreseen. Celestia looked on as the stallion she loved struggled against his chains to no avail. Had he the free reign of his magic, he'd have most likely tried blasting her then and there. Thankfully, Celestia had placed enchantments upon him, not unlike those used on the unicorns watching the Equestria Games, in order to temporarily prevent him from using his magic. Instead, she looked on, her eyes never leaving him as he growled within his muzzle.

"Sombra...it's me."

The dark stallion said nothing, his green eyes just staring at her with intense hate. She never wanted to have to see him like this, so twisted from what he once was, but if there was anything she could do for him, she knew she had to try. So, she began to approach, willfully oblivious to the thrashing Sombra was using against his binds. Kneeling down onto all four knees, she looked upon him again, her expression one of melancholy.

"Please...if there's anything of the stallion I love in there...let me know."

But no reply came. Instead, the unicorn before her just kept on struggling, his expression never changing from that of utter loathing. As she gazed upon him, it became clear that words alone were not going to help him. Instead, she let out a long sigh as her horn began to glow. Seeing this, and fearing an attack, Sombra instinctively pulled harder at his chains, even though he knew from his past attempts that no amount of strength would break them. Celestia lowered her horn towards him as it's glow brightened even further. There was a blinding flash of light, and Sombra's eyes shut tight.

As the light faded, Celestia raised her head again and looked at the stallion, whose head was now hanging low and showed no sign of struggling anymore. She tilted her head, waiting for him to do something, anything. And soon enough, he did. The stallion began to move, albeit slowly, with his chains chinking with every movement,. Raising his head, his eyes opened, and when Celestia saw them, her expression became one of joy. For those were not the dark green and hateful eyes of the Sombra that had been here moments before. Those were his true eyes, those of any other pony, save for his distinct blue irises.

Celestia's own eyes began to well up at the sight of him like that, but they were tempered by him suddenly looking both frightened and confused, as he tried speaking before his muzzle muffled his words. Smiling, Celestia raised a hoof and unclasped the brace on his neck, allowing the muzzle to fall to the ground. His mouth now uncovered, Sombra looked at Celestia, his face still one of confusion, and spoke.

"Ce...Celestia?"

The sun Princess smiled back at him.

"Yes, my love. It's me."

Sombra's eyes remained confused, though only for a moment, as they soon widened with shock and horror. Celestia knew that expression well, as she realized that he was suddenly remembering everything that had happened. Him taking the dark magic into himself, and everything that happened since. She gave him all the time he needed to let he matter sink in, before Sombra raised his head to look at her again.

"What...what did you do?"

She smiled again before moving forward, nuzzling her head against his own.. It was a pleasant feeling, and one that caused Sombra to close his eyes as he allowed the comfort of the moment to wash over him. In this tender embrace of his love, Sombra heard her words.

"Just as night gives way to day, so to can the shadows in one's heart be driven back by light."

The stallion felt his heart lift, feeling that maybe, just maybe, the mare of his dreams had freed him from the terrible curse that he'd willingly taken into himself. But that feeling was dashed when he heard her next words.

"At least...for a time."

After a few moments has passed to allow himself to fully grasp her words, Sobmra understood fully. Whatever she had done to him by way of her magic, it was not permanent. At best, the darkness within him had been pushed back, at least far enough for him to allow some control over himself as he used to. That knowledge tainted the pleasant moment he was sharing with Celestia, but even so, he wanted this. He wanted to be with her more than he could possibly say, and through her, he had been given this opportunity. But Sombra was never one to simply lose himself in a moment like this, and though he would like nothing more than to stay like this with her, he knew that there was an important matter to discuss.

So, as he pulled away from her, greeted now by a concerned look on Celestia's face, he spoke.

"Celestia...what are you planning? Why did you bring me here?"

Celestia's expression was hard to figure out. Shame. Sadness. Confusion. Uncertainty. All these and more were present in her face as she spoke.

"I needed...I couldn't leave you there. Corrupted...trapped by the darkness you took from the other me and her sister. I had to do something. I had to try!"

Sombra looked at her, heard the earnestness in her voice, and sighed, giving a warm smile. He knew that what she was doing was done out of love. She cared for him deeply, and he knew that she meant what she said. This mare would probably go on for years, trying to help him, to free him of this darkness, all because of how much he meant to her. But, although he appreciated what she was doing for him, he could not help but feel pained at this. A point he was more than willing to voice to her.

"Celestia. Please...listen to me."

The sun Princess looked at him, her face bearing a look of concern.

"What is it?"

Sombra looked away from her briefly, his expression that of great discomfort. He knew she wasn't going to enjoy hearing this, but nevertheless, it needed to be heard.

"This...curse, in my heart. The darkness I took into myself. I have had enough time to feel it to know one thing and one thing only."

His expression changed to one of utter seriousness.

"That it can't go away."

Celsstia looked at him with a horrified look on her face, shaking her head as though silently refusing to believe what he'd just told her. Even though he hated seeing her like that, Sombra carried on.

"No magic, in my world or yours, can remove this blight from my soul. it is a part of me, now and forever. And though your magic has pushed it back, I can already feel it growing in strength. It will take me again, Celestia, and you can't do that spell on me forever."

Celestia stood tall again, looking down on him with a face filled with determination.

"That doesn't matter! I will try! We all will! If there is one thing I have learned, it's that evil never lasts forever. It can be driven out, just like it was with my sister."

Sombra stared at her intently, and knew in his heart that she fully intended to go through with this plan, to spend her every waking moment trying to find some means, some cure, for his condition. He wanted to be free of it, that much he could not deny. But Sombra was an honest pony, and that honesty allowed him to see a matter that Celestia, in her passion, had perhaps failed to remember. It brought him no joy to say it, but if he was going to convince her of the folly of her quest, it had to be said.

"Celestia...the Sombra of your world...was he saved?"

The Princess opened her mouth, ready to say something to refute his words. But she couldn't, for she knew he was right, even though she wanted nothing more than for him to be wrong on this. But it was true, the Sombra of her world was tainted with the same darkness that this Sombra now suffered with. That darkness had corrupted and twisted him to the point of no return and, to her everlasting regret, had resulted in his death. It was the one time she had never allowed herself to enjoy a victory over evil, and she knew why her love was saying this.

"Sombra...I can't just give up! There...there has to be a way!"

The stallion looked at the ground. He hated himself for doing this to her, to tell her that there was no hope for him. If their positions had been reversed, he had no doubt that he would do everything in his power to help the mare he loved, no matter what those around him would say against the idea. But he knew, even now as he wracked his brain for a solution, that there was no way of removing this evil that now lay at his heart. Eventually, that hate and fear would return to the forefront of his mind, and he would once more be the same tyrant that this world was rid of not so long ago.

But, as he dwelt on that, another thought came to mind. It shocked him the moment he thought of it, and at first he tried to banish the very idea of it. But, as he looked upon Celestia, and knew that she would remain with him no matter the danger, he felt himself giving in to the idea that now grew in his mind. His face became that of fear and shame, a look that Celestia was quick to pick up on. She stepped forward, her face one of concern, as she awaited him, knowing that he was about to say something. But the words that came out of his mouth were not what she was expecting.

"There...is...an option."

Celestia's eyes widened as she drew closer to him, hoping beyond hope that he might have figured something out. That only made him feel worse about what he was about to suggest.

"It's not a solution. But, for me, it is...an escape."

The sun Princess tilted her head, clearly confused by what he was saying. But Sombra remained silent, staring at her with great pain in his eyes, as though he was ashamed of the words he'd just spoken. As Celestia continued to look at him, a brief spark of understanding began within her mind. As the moments passed, her face morphed, from one of confusion to one of horror, as she began to back away from Sombra, who now looked away from her, knowing she'd figured it out. Celestia meanwhile was shaking her head ferociously, her eyes welling up again.

"No...NO!!!"

It was here that Sombra spoke again, his voice quiet and subdued.

"I would never say such a thing unless I had no other choice before me. And, in this...I don't."

Celestia kept shaking her head, but now moved towards him again, kneeling down once more as she began to nuzzle him.

"Don't say that! There has to be a way to help you! You...you can't...!"

Sombra shut his eyes tight, the comfort of feeling his love's head against him again giving him a brief respite from the horror he'd found himself in. But he couldn't be dissuaded. Not now.

"Celestia...the darkness in me cannot go away. It can only...end."

The Princess said nothing, but Sombra didn't need much imagination to know just how hurt she was feeling right now, and it was all his fault, for which he would forever hate himself. Even so, he kept on speaking.

"If I stay here, you can only ever know me as a stallion who has fallen. I would be a twisted fiend, who lives only for the sake of hate and destruction. If I roam free, I would be a plague on this world, just as the two sisters of my world were when they were corrupted."

He pulled away from her, and it was here that he saw that Celestia's eyes were already overflowing, her cheeks now drenched in her tears. It broke his heart to see her like that, but he carried on regardless.

"Celestia...we all do what we must to ensure harmony reigns, in this world or mine. You banished your own sister to the moon to prevent eternal night. You trapped Discord in stone to halt an age of chaos. Your student and her friends even destroyed the Sombra of this world to keep the Crystal Empire safe."

His expression became a grim one.

"And now...I too must do what is needed...to ensure that a great evil is destroyed."

Celestia shook her head, albeit slower than she'd been doing before.

"But...what about...us?"

Sombra's expression softened a great deal as he pondered those words. It would have been an utter lie to say that there wasn't some small part of him that was tempted to avoid this terrible plan, if only so he could continue to be with her. But, as he steeled himself, knowing that what he was suggesting was the only path, he put on a smile for her.

"Celestia...for a long time, my reign in the other world was plagued by the evils unleashed upon it by the two corrupted Princesses. Each day was a trial, a battle. And then..."

His smile then became a genuinely warm one.

"...you came. When the two of use grew closer, I could allow myself to think, just for a moment, that the world would be alright again. When I was with you, both then and now, I felt at peace like I've never felt before. You gave me hope, and light and love in a time of darkness and chaos. And for that...I will always love you."

The elder alicorn heard each and every word as though he were reaching into her chest and holding her heart warmly in his hooves. Celestia could not wait one moment longer, and she moved her head forward, locking her lips onto his before he could say or do anything to stop her. But, soon enough, the two both closed their eyes as they felt the warmth of their lips upon one another. It was, for lack of a better word, bliss. Neither of them had felt such contentment and joy for a very long time, and here, in this moment, the two of them just felt right.

But, this moment could not last forever, and soon Celestia moved away from Sombra, ending their kiss. As the two gazed into each other's eyes, Sombra's expression grew grim once more.

"You know as well as I do, that if I allow this darkness to continue on...if I ignore my duty to rid the world of evil, just to preserve my own life...I would take that first step to being the tyrant that died in this world."

He looked away from her, his face still one of determination.

"I will not allow that. I will end the darkness, and myself, together."

The Princess shook her head, refusing to accept what her love was telling her. Sombra, looking at her, knew that this was what she was thinking, and sighed before speaking.

"Celestia...you deserve to be happy. You deserve to be able to move on. You deserve...better than a cursed stallion."

The alicorn frowned at that, her eyes still welling up.

"Others may come...but they'll never mean as much to me as you."

Sombra put on a warm smile for her.

"Hearts will heal...and their scars will fade."

Celestia looked upon the stallion she loved, and felt utterly trapped. She knew she could not talk him out of it, and worst of all, there was a part of her that actually agreed with what he was saying, no matter how horrible it was to hear. He was right, there was no happy ending for him here, and even if he lived, he would be bound to that darkness forever. A darkness that only took him because her life had been at risk when facing the other Celestia within that other world. He'd sacrificed himself for her, and now, he planned to sacrifice himself a second time, for the world.

Looking upon him, at the regretful look on his face, she slumped her shoulders, her face that of defeat. In no other time in her life would she consider this, but now, she felt she could do nothing else.

"Let me do it."

Sombra's head snapped in her direction, his expression one of shock.

"WHAT?!"

The distress in his voice was clear, and Celestia knew what must have been going on through his mind. He would have said something like she should not do it, so as to not sully her hooves with this vile act. But the last thing Celestia was willing to do was to let the one she cared for so deeply to do something as tragic as take his own life. Before he could speak further, she raised a hoof and placed it on his mouth. He looked into her eyes, those beautiful eyes he'd learned to love so much, and listened to her speak, in that calm and motherly way she was so famous for.

"I brought you to this world in the hopes of freeing you. But...it is as you say, that you cannot be free of this. And you're right, this will end your suffering. My mistake led you to this..."

She put on a smile, though whether it was forced or genuine, Sombra could not say.

"...let me be the one to help you, one last time."

Sombra looked at her, still not believing what he was hearing, and knew that she could not be deterred by his words. He perhaps should have known that Celestia would want to aid him in this, even though it would break her heart to do so. He silently cursed himself, thinking that perhaps it would have been better if she'd never met him, never fallen in love, never put herself in a position to be as hurt as she would be by this. But it was too late for regrets now. All that was left was this offer. This mare, this Princess, this angel, would be the one to give him the only release anypony could from the darkness that now ruled his heart.

So, looking at her now, he let out a long sigh, and nodded gravely. Celestia's smile faded, knowing what she needed to do, though would never forgive herself for doing so. She looked on as Sombra raised a hoof to his chest, placing it on one of the many chains that bound him, and pulled down, exposing a bare section of his chest, where Celestia knew would be the place his heart was. The two lovers looked at each other one last time, and in that moment, so many feelings past between them. Regret, love, and so many others beyond counting. Their time together had been brief, but they knew that no matter what, they would forever be a part of each other's lives.

Looking down at Sombra's chest, Celestia began to focus her magic into her horn, and began to lower it. Sombra, seeing this, took several deep breaths, preparing himself for what he now knew was the end of his life. Celestia would have never wanted to do this to anypony, least of all the stallion she loved, but now she had to, and as the tip of her horn came into contact with his chest, she shut her eyes tight as her magic continued to build. Her eyes welling and overflowing with tears, she heard one final utterance from her beloved.

"Remember, Celestia, in this life and the next...I will always love you."

With those final words spoken, Celestia too took several deep breaths before shutting her eyes even tighter, opening her mouth and letting out an ear-piercing scream as she discharged her magic. There was a blinding flash, and when it was done, Celestia heard the heart-shattering sound of a body falling to the ground. She feared what she might see, but opened her eyes nevertheless. And there he was, Sombra, lying on the ground, unmoving. His chest bore the still-smouldering mark of where she'd struck him, right in his heart. Looking upon his now-lifeless face, Celestia saw a look, not of pain, but of contentment.

Before she could do anything, she heard the sudden sound of the chamber's door bursting open. Turning her head, she saw Luna charge in, no doubt here due to Celestia's scream. It only took a moment of glancing a both Celestia and Sombra for Luna to understand what had happened, as she raised a hoof to her mouth to stop a gasp from escaping. But Celestia turned away from her sister and towards Sombra, as she knelt down beside him. Raising a hoof, she placed it upon his still-open eyes before closing them, giving him one final act of kindness. As she stared at him, knowing she would never see him again, the tears returned in droves, as she leaned forward and gave him one final kiss upon his forehead, before speaking the last words she would ever say to him.

"Farewell...my love."