Canterlot Castle
Celestia sat at a table overlooking the royal gardens enjoying a slice of cake as she enjoyed the view. "Hmm! Lemon!" However, Celestia's moment of relaxation was interrupted when she felt a magical disturbance. And upon sensing the source of it, her eyes went wide. "It can't be..." Celestia picked up on where the disturbance was originating, and found Mirror Sombra before her eyes. "S-Sombra? What are you doing here?"
Mirror Sombra let out a bitter chuckle. "I wish my visit to your world was for a better reason. But I need your help." The two rulers then walked as Mirror Sombra recounted the events that had led to this moment. "As of late, you and Luna's counterparts have been quite the inconvenience for my kingdom. However, a new player has entered the battle under their employ. Recently, I had gathered my forces to meet the dark sisters in battle. However, the enemy that awaited us was a lone figure." Mirror Sombra briefly shivered for a moment. "And this lone combatant managed to incapacitate me and most of my forces. And the most terrifying part is that he said there were more like him under the employ of your counterpart." Mirror Sombra then turned his gaze to the floor in shame. "And upon thoroughly trouncing us, he told me that he'd soon return. As well as leaving his name. Burst Stream."
"Burst Stream..." Celestia whispered to herself before returning her attention to Mirror Sombra. "Alright. I'll help you. And I know just the people who can be of some aid to you."
Mirror Sombra smiled. "Excellent. Now then. Shall we leave?" Sombra gestured in the direction of the mirror he came through.
"No." Celestia said as she shook her head. "I think it would be best if you meet with the people who will be aiding in your battle. I know them very well. They're some of the strongest warriors I've seen in many years. And they've also fought alongside and saved the Bearers of Harmony as well. As well as fight against some of the deadliest enemies we've seen here. One was even bold enough to punch Discord right in the face."
Mirror Sombra was in awe. "Truly these warriors must be the greatest heroes of your kingdom."
"Well, they're called the Elements of Heroism for a reason." Celestia said with a giggle. "And I happen to be in close contact with one in particular." Celestia took out her phone, and texted Burst Stream. "They'll be assembled in Ponyville within the hour or less. Also..." Celestia summoned a scroll, and a pen. "I'd better alert Twilight. My former student. Now my fellow princess. She and her friends will certainly be of help in the coming battle." Celestia quickly sent the message via magic. "Now. I believe it would be rude to keep them waiting too long. Hold onto me tightly."
Mirror Sombra smiled. "I've much experience doing that dearest." And with that, Sombra wrapped his arms around Celestia tightly.
"Yes. I'm aware..." Celestia said with a nervous look as she and Sombra were soon wrapped in the golden glow of her magic. Teleporting to Ponyville! Upon arrival, they saw a lone figure approaching them. "Sombra. I'd like you to meet the leader of the Elements of Heroism."
Burst smiled, but soon had a puzzled look on his face when he noticed Mirror Sombra. "Celestia? This guy looks just like Sombra. Who is he?"
"I am Sombra. Though not the one you are acquainted with." Mirror Sombra answered. "I come from a different Equestria. One that is a dark reflection of this world. " He then looked over Burst Stream. "You certainly look the part of a hero. Might I have the name of the one who's lead the brave number of heroes to protect this world?"
"Burst Stream. Element of Power." Burst answered. "Nice to meet you."
Mirror Sombra was taken aback by Burst's answer. However, he quickly regained his composure and noted Burst's appearance. Unlike his mirror counterpart, this Burst had an overall cleaner appearance. His clothing choice was vastly different as well. Unlike the tattered black coat the Mirrror Burst wore, this one wore a white coat that was in fair condition. Also of note was that his wings were a mix of dragon and angel features, and that his hair was shorter. In short, his appearance just screamed "hero". "I suppose I could say it's the first time it actually is nice meeting you."
Burst blinked. "I'm guessing you came here because you got your butt handed to you by the mirror version of me?"
"How...how did you know that?!" Mirror Sombra asked.
Burst shrugged. "Eh. When you've read as many comic books as I have, sometimes you tend to put two-and-two together when it comes to mirror worlds. The others should be arriving shortly. They're grabbing their weapons too. Don't know what our enemies are packing." A small chuckle escaped Burst's lips. "After fighting my own dark side, I've been wondering what it'll be like to fight myself." Burst then noticed the rest of his friends approaching. "Looks like we're all ready now."
Mirror Sombra was amazed at both sets of elements assembled. "This is perfect! With your help, victory is certain!" Mirror Sombra then turned to Celestia, and smiled lovingly. "I knew you would be of help. Especially for all the happiness you've given me." He then took hold one of Celestia's hands. "My dear, sweet Tia..."
Burst took note of how friendly Mirror Sombra was getting with Celestia. One of HIS current girlfriends. And he raised his brow in suspicion. Inferno noticed Burst's mood, and decided to intervene. "So...how do we get to your world?"
"There's a mirror back in Canterlot that will lead us to my world." Mirror Sombra answered. "And we'll be headed there immediately. Let's not delay." A massive group teleport was initiated, and the group was transported to Canterlot Castle. Mirror Sombra led them to the mirror. "Here we go..." Mirror Sombra stepped through the mirror first, and the rest of the group followed. Upon reaching the other side, the two sets of Elements were amazed to see that despite this being a reflection of their own world, that it was largely the same. Save for the figures that greeted Mirror Sombra when they arrived. "I'd like you all to meet my council." Mirror Sombra then pointed to each of his council members." Justices Flim and Flam. Scholar Derpy. Duchess Chrysalis, and Princess Trixie." He then smiled. "Sorry to have worried you my friends. But I assure you that my absence has brought us some much needed assistance."
Mirror Chrysalis noticed Celestia. "As well as returning your heart to its usual shine." She said with a giggle.
"Indeed." Mirror Sombra said with a nod before walking over to Celestia. "It's been far too long dearest. I've missed you so much..." And Mirror Sombra kissed Celestia. Both sets of Elements were shocked. However, they all backed away from Burst when they saw his eyes shrink to pinpricks.
Burst stood completely still for a moment before slowly advancing towards Celestia just as she pullled Mirror Sombra off of her. "Excuse me. But could you tell me what reason you have for kissing her?" Burst asked calmly.
"Oh? She never told any of you?" Mirror Sombra asked. "Dear Celestia and I were a couple a thousand years ago."
Burst was shocked. "....Well, maybe she hasn't told you about me. Currently I'm the one who's dating her and Nightmare Moon."
"My apologies." Mirror Sombra said with a small bow. "But surely if you have two girlfriends, you could spare me my dearest?"
Burst narrowed his eyes, and looked Mirror Sombra right in the eye. "I made the mistake of letting her go once. To someone who appeared civil like you, but was little more than a monster. One that used her to try and emotionally destroy me. And I'm not going to make that same mistake again."
"I assure you my friend." Mirror Sombra said calmly. "I would never do anything to harm her so. I...could never imagine doing so much harm to her."
Burst groaned. "If you love Celestia so much, why haven't you tried to form a relationship with this world's Celestia?"
"If only you knew." Mirror Sombra said sadly. "My world's Celestia is the complete opposite of yours. As cruel as yours is kind. I honestly could never see myself loving someone such as her."
Burst frowned. "Then maybe you could change her." Burst then gestured to the Elements of Harmony. "I've seen these girls reform those who were thought to be beyond saving." His mind then flashed to Moon. "I've even helped someone move on from a dark chapter in their lives."
"There is no changing her." Mirror Sombra answered. "I've pleaded with her many times to change her ways. But my words are wasted on deaf ears."
"You really think that's all it takes? Words?" Burst said. "You need to do actions to back them up. Maybe you just haven't tried hard enough! Or maybe..." Burst then shifted into his nightmare form! Staring Mirror Sombra down! "You're just too scared of your own dark side." The whole room was silent. And Mirror Sombra was rooted in place with his face frozen in shock. "Huh. Didn't expect that to-"
"GUARDS!" Mirror Sombra screamed as the doors burst open with whatever active guards stormed into the room! Surrounding Burst! "KILL HIM!" All of the guards raised their spears at Burst!
Burst blinked. "Whoa. Could all of you just chill for a moment?" One of the guards jabbed their spear at Burst! "Hey!" Burst exclaimed as he stepped back! "What's the deal?!"
"The 'deal' is you!" Mirror Sombra snapped as he pointed at Burst! " How did a being of darkness like you come to be so close to my sweet Celestia?! That very form, it's clear you've been ensnared by the power that once held control over the sister of my beloved! I'll not allow you to harm her!"
Burst sighed. "I really don't wanna do this. But you're not givng me much of a choice." Burst pulled out Bahamut Aether from his belt, and activating it! The blue blade of light making the eyes of his nightmare form glow slightly. Burst then slashed at the bladed potions of the guards' spears! Leaving them little more than sticks. "I don't want any of your to get hurst. Please. Just back away now." The guards were a bit shocked at hearing this, and backed away slowly. Some of them stumbling backwards as they backed away. Burst then turned his gaze to Celestia. "Celestia? Could you tell me why your ex sicked his guards on-?!" Burst leaped back to avoid a massive blast of magic! He then saw Mirror Sombra's hand smoking from the blast!
"I won't let you lay a finger on her monster!" Mirror Sombra spat as he summoned a crystal cage to protect Celestia! "You'll have to get past me if you want her!"
Burst blinked in confusion. "What are you talking about?"
"I know all too well about the power and madness that form brings!" Mirror Sombra scowled at Burst! "The same power that drove Celestia's sister mad! And now it seems that you've been consumed by it as well! How could she ever love a beast like you?!"
Burst took a deep breath before getting into a fighting stance. "Looks like we're doing this the hard way. Time to see what you're made of."
"I'll show you!" Mirror Sombra summoned a sword made out of magical crystal! "My sword shall pierce that dark heart of yours!" Mirror Sombra charged at Burst! Swinging with as much force as possible! However, Burst blocked every one of his strikes!
"You're not focused." Burst noted as he raised Bahamut Aether to block another strike. "Losing composure in a fight can put you in a pretty bad position."
Mirror Sombra glared at Burst! "Don't you dare lecture me about composure!" He then fired a blast of magic! Which Burst deflected by using his sword's light blade! "WHAT?!" Sombra was then sent flying by a shot from one of Burst's Twin Burst blasters! But Mirror Sombra was far from finished! I don't have to beat him. I just need to stall him! Mirror Sombra slowly got to his feet. Seeing Burst waiting for him. "You seem to be quite courteous despite your darker impulses in the driver's seat." Mirror Sombra then noticed his council channeling the experiemental magic he'd been developing. "However. I believe this is my victory."
Burst was confused. But was soon he screamed in pain! "AAAGH!" Burst was hit full force with a blast of harmony magic! Still in his nightmare form, and knocked out cold from the blast!
"Take him to the dungeon." Mirror Sombra commanded a few of the guards. The guards put cuffs on Burst, and escorted Burst to the dungeon. Mirror Sombra then deconstructed the crystal cage around Celestia. "Worry not my dear. That monster won't troubly y-"
"What were you thinking?!" Celestia demanded! "Burst wasn't trying to hurt anyone!"
Mirror Sombra blinked. "But...that form-"
"Is one he's used before." Celestia answered. "In fact, the first time he gained that form was just so he could protect me. And he's been in complete control of it." Celestia sighed. "Darkness isn't as evil as you think it is. Just what about Burst using this form gave you reason to react so unstable?"
Mirror Sombra shook his head. "It's nothing. Nothing at all."
Mirror Canterlot Castle. Dungeons.
"Nnnghh..." Burst groaned as he woke up. He then noticed that he was in a cell, his hands cuffed together, and still in his nightmare form. "Well, never expected to wind up like this." Burst muttered to himself before looking at the two guards. "Could you two move aside? I don't want either of you getting hurt."
One of the guards scoffed. "Not likely monster. You've been rendered powerless by the harmony blast the council was developing."
Burst sighed. "Why do I have to prove you wrong?" Burst then broke his cuffs as he rose from his seat. Both guards were speechless! "Now. Please move aside." The guards nodded slowly. "Thanks." Burst then kicked the cell door down, and summoned his Duelist Arms back to him. "All I need now is directions to the throne room." One of the guards nervously handed Burst a map of the castle. "Oh. Thanks dude!" And with that Burst followed the map back to the throne room. "Hey everyone! What did I miss?"
"I was being read the riot act." Mirror Sombra answered. "It's clear that I jumped to conclusions regarding this dark form of yours. I apologize."
"Cool." Burst answered. "So. Why aren't you interested in this world's Celestia?"
Mirror Sombra sighed. "As I said before. She's cruel and has constantly tormented my kingdom."
"But was she always this way?" Burst asked. "I can tell that's not the only reason you're hesitant towards her." Burst slowly approached Mirror Sombra. "Like I said. Maybe you could be the one to change her."
Mirror Sombra sighed. "She is unwilling to change. I've already told you that."
"No. That's only half of it." Burst said with a frown. "That's not the only reason you've failed to get through to her. You've got yourself to blame as well. Because you're afraid, aren't you?" Burst looked Mirror Sombra right in the eye, and nodded slowly. "Yeah. I see it now. You're scared she'll bring out the side of you that you don't want to think about. Because she's what you think you will be if you give way to your darker side. The side that you choose to ignore."
Mirror Sombra snapped his head in Burst's direction. "Yes. I AM afraid. I've been afraid for so long! Ever since Celestia told me of your world's Sombra! How he became a tyrant because he gave into the darker impulses within him! How he made many suffer! And when I see my world's Celestia, that fear is magnified! Because I'm afraid I'll turn out just like him!"
"Oh for the love of-!" Burst facepalmed. "You want to know how I got my nightmare form? I didn't get it by being scared of my darkside. Or trying to repress it. I got this form because I made my peace with the darkness inside me. What you're doing to yourself? It's only going to make things worse for you." Burst sighed. " To deny that your dark side exists, it's the same as denying a part of you. Sure. It can give you some pretty negative suggestions. But if you're willing to talk things out with it, you'll be surprised its more than willing to listen. That's why I can access this form so easily. Because I accept that my dark side is a part of me. And upon this fact, you make me sick." Burst stared coldly at Mirror Sombra. "It's easy to see why Celestia fell for you. I even got a little jealous that I wasn't the first one to make her so happy. You're a good ruler, and an even better guy. But how can you claim to be better than the villains you're fighting when you're too scared to face your dark half?" Burst then walked up to Mirror Sombra, and stared him down. "How could I ever be jealous of a glass king like you?" Burst then turned to Celestia, and his gaze softened. "We'll talk later." Burst then returned to his regular form, and walked out.
Celestia looked to Mirror Sombra. "Why did you hide this from me?"
"Because I was afraid you'd hate that part of me." Mirror Sombra answered shamefully. "You made me so happy. And I never wanted to lose you. Because I love you so much."
Celestia sighed. "I loved you too. But how can I love you if you're so scared to accept yourself?" Celestia looked sadly into Mirror Sombra's eyes. "You want me. But I don't know if I'm the one you need." Celestia then turned to leave. "But Burst needs me now. And I want to help him. Help I'd have been more than happy to give you if you were willing to show me all of you."