Ponyville.
Princess Luna was an example of the wrong place, wrong time saying. If she had arrived in Ponyville a few minutes earlier, she would have seen Solomon Grundy destroy the town and would have been able to help Batman and the mane six defeat him. However, that didn't happen, so all she saw when she entered Ponyville for her holiday was destruction and bodies everywhere, with a giant bat creature standing in front of the weary Elements of Harmony. So she did what anypony in her situation did.
She attacked.
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Batman rolled to recover from the surprise attack from behind. Turning to face his attacker, he was stunned at what he saw. It was a midnight blue pegasus, but it had a unicorn horn and was only a few inches smaller than him. Her mane looked like a constellation in the Milky Way. She had an air of royalty about her, which probably made her one of the princesses he heard about. He threw himself out of the way of another magic blast, one that turned the rubble it hit into ash. Whatever she was, she meant business. Since he was still tired from the battle with Grundy, she was the last thing he needed.
"HOW DARE YOU ATTACK OUR SUBJECTS!" Princess Luna roared in the Royal Canterlot Voice. She sent blast after blast at Batman, who managed to duck or dodge out of the way just in time. The mane six rushed to Luna, trying to get her to stop.
"Princess Luna, you don't understand, it-" Fluttershy began, until a sphere of purple magic enveloped her and the other five.
"Do not worry my friends, this barrier will keep you safe until we defeat the beast!" With a yell, Luna charged at Batman, completely oblivious to the protests of the six ponies. Batman threw a batarang at her head, only to frown as it bounced off a barrier. Luna laughed at his attack.
"Do you think that your puny toys could hurt us? You are pathetic." Batman let three more batarang fly, all of which bounced off her invisible shield. Luna used her magic to levitate some of the debris to circle around her, before tossing them at Batman. He pulled out the REC launcher and began to weave in and out of the debris storm, taking pot shots all the while. The REC charges were simply absorbed by her barrier, while the debris got closer and closer to hitting him. Diving behind an overturned vendor stand, he pulled out three more batarangs, this time with an anti-rang among them. After his first two attempts, he believed the horse would think her barrier would stop all his projectiles. She was in for a surprise.
Vaulting over the stand, Batman let the three batarangs fly. As Luna continued to shoot magic at him, she was oblivious to the three projectiles heading to her. The first two bounced off her shield, but the third sliced right through and smacked her on the horn. The rang did its job and temporarily de-activated her magic. Luna tried in vain to get her horn to work, unable to produce any of her great magic.
Seeing his chance, Batman closed the distance between him and the princess. She lashed out with a fore hoof when he got close, which he easily ducked and responded with a hard uppercut to her sternum. Hearing a "oomph", Batman continued the assault. A shot to the leg, a jab to the ribs and a head-butt was enough to daze the princess. Batman grabbed her neck and spun, throwing the horse onto the ground. He leaped into the air to finish her with a ground pound, only to watch her roll out of the way. She stood up and glared at Batman, seething with rage. With all her effort, she began placing power into her horn. The effects from the batarang had worn off and Luna took advantage of it. Her horn crackled with power as she faced Batman.
"We've had enough, creature!" she spat, "Now you fall."
Batman braced himself for her attack. Remembering the spell Twilight had used in the forest, Batman calculated he had about two seconds to move before the spell reached him after she fired it. That would be plenty of time to get out of the way.
"Whoa, you were right Scootaloo, he is real! I'm so glad we came back to watch!"
Time slowed down as Batman felt his heart drop into his stomach. Slowly, he turned his head to look behind him. There, about twenty feet away, were three fillies. He recognized Scootaloo, but not the other two. The ponies had begun to come back into the town, believing the battle to be over with the arrival of Luna. His eyes widened as he realized that the three fillies were in the line of fire. Luna, unaware of the CMC, chose to fire her spell while Batman was distracted. Batman turned and watched as the spell slowly got closer, considering his options. If he dove out of the way, he would survive, whereas the fillies would surely die. If he took it head on, there was a good chance he would die. It was no choice.
Batman crossed his arms over his chest right before the blast connected. He had expected pain, but what he got was far worse. Batman roared in pain, his body burning as if it was on fire. The suit managed to prevent the pure magical energies from killing him, but the force of the impact rocketed him across the battlefield and straight into a metal poll. He felt his head bang against the poll, then everything went black.
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Luna paused for a moment, breathing heavily. Her spell had launched the bat into a pole, where it now lay, unmoving. She walked over to it, surprised to see it was still breathing. Her horn glowed once again as she aimed it straight at its head, prepared to fire, until...
"Princess Luna, wait!" Fluttershy yelled, flinging herself between Luna and the bat. Luna's shield had fallen when Luna used her last attack. Twilight and her friends had been watching the entire battle, so the moment the shield fell, Fluttershy stepped in to stop Luna from killing the bat.
"Fluttershy, get out of the way. This creature is dangerous and must be dealt with." Luna responded, trying to get past her.
"You don't understand, Princess. The bat isn't really bad," Fluttershy said to her, desperation in her eyes.
Luna paused momentarily, surprised at what Fluttershy said. "Elaborate."
When the other five arrived, Fluttershy began to tell Luna what had happened, from their battle in the forest, to his saving Twilight from Grundy. It had taken some convincing for Luna to believe something like that existed, but looking at the destruction, she couldn't deny it. As Fluttershy and her friends talked, Luna's frown grew deeper and deeper. She didn't know what to make of the bat the creature that she considered evil. But she knew some pony that would.
"Very well, we shall take it to Celestia." Luna covered all of them in her magic, teleporting them to Canterlot.
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Canterlot, Dungeon.
The first thing Batman noticed when he woke up was that he hurt. A lot. The next thing he noticed was that he was in a prison cell. It was an old fashioned cell, with the rusty bars and the flat bed. The bars were so bad that he probably wouldn't need his belt to get out. At the thought of his belt, he looked down and saw that the horses had left it on him. His respect for their intelligence went down again.
He was still debating if he should try to escape or wait and see what they were going to do to him, when the door to the dungeon swung opened and the princess from earlier walked in. She walked right to his cell and looked through the bars at him, anger in her eyes. Well, her good eye, as her right one was swollen from where Batman had head-butted her. She pulled up a chair and sat down, glaring at him.
"We'll be blunt, creature. We know you are intelligent and we know you can talk. This is an interrogation and you WILL answer our questions. Understand? Question 1; why did you fight against the creature known as Grundy?"
Batman walked over to the bed and sat down, looking the horse in the eye. Instead of answering, he chose to remain silent, angering the princess even further.
"Your silence does not help your cause, creature," she angrily said. Something about him just made her furious. The princess didn't like a second creature of the night in her castle. "Do you not know who we are?"
"A unicorn bitten by a radioactive pegasus?" he guessed dryly. The joke did not go over well with Luna.
"We are an alicorn, an old and powerful race. We are called Luna, Princess of the night and mover of the moon!"
Batman raised an eyebrow at this. She could move the moon? It would require a lot of power to do that. Then again, Superman could do it, so maybe her statement wasn't complete bull.
"So you rule over the horses." he muttered to himself.
"You really are slow, aren't you? My sister, Celestia shares ruling with us. She takes the day, we have the night. Everypony knows that."
"I take it she moves the sun then?" Batman said in a carefree voice.
"You aren't as dumb as you look. Yes, she is Princess of the sun and you will show her respect when you meet her."
"So we must be in that giant castle I saw on the mountain."
"Canterlot. We thought ever creature knew of it. Guess not," Luna said mockingly.
As much as Batman hated her attitude, he continued.
"So the guards I fought were royal guards. Don't bother answering that one, I know I'm right. The only thing I'm not entirely sure of is where we are?" he asked, feigning ignorance.
"We are in the continent of Equestria, home to all types of ponies, griffins and dragons. The entirety of which is ruled by us and our sister. That's right, we rule over a continent. What do you think of that, creature?" She jeered. To her surprise, Batman smiled.
"I think this interrogation has gone very well. I did not know some of the things you told me, but thank you answering those questions. Anytime you want to start your questioning, go right ahead," he chuckled and leaned back against the wall. It took Luna a few seconds to realize what he was hinting at.
Her face turned bright red as blood rushed to her face. She got close to the bars and began to flood magic through her horn, when the prison door flew open and a guard stepped in.
"Princess Luna, Princess Celestia is ready to meet the bat now."
"Well creature, it seems you will face my sister sooner than expected. We hope you’re ready." Luna said, opening the cage door.
The guard walked over and put hand cuffs on Batman, before he and Princess Luna started to walk up to the throne room. Batman broke the locks with ease, but kept the cuffs on, deciding to save that surprise for later. The three of them walked out of the dungeon and into the palace. Batman would be lying if he didn't say he was impressed.
The entire palace was made of white marble and gleamed as if it was its own sun. The decorations were nice, but not the overwhelming kind you see in most castles. Every inch of it was clean and bright, so clean that Batman wondered how Alfred would react if he saw this. He'd probably be able to find some microscopic bit of dust. After a few steps, about twenty more guard horses showed up. At least the guards had brains. They walked all through the castle until they reached a pair of giant, oak doors covered in gold, which swung open to reveal the throne room.
Looking around the room, Batman saw the six horses from earlier., Twilight, Applejack, Rarity, Pinkie, Fluttershy, and Rainbow Dash. They all eyed him curiously, except for Fluttershy, who hid behind her mane. There were windows and a red carpet, but what really caught his attention was the horse on the throne. She was the same species as Luna, except with a white coat and at least a foot taller. She radiated power and had an air of leadership. Batman instantly placed her as Princess Celestia.
The guards and Luna knelt upon enter the room, but Batman remained standing. This did not go unnoticed be the guards.
"Kneel before the her Majesty," he said, hitting the back of Batman's knee. Batman responded with a kick to the jaw that knocked some of the guard’s teeth out. In an instant, ever guard in the room had surrounded him, poised to strike, until a voice talked them down.
"Lower your weapons and please back away," Princess Celestia asked. The guards begrudgingly backed off, letting Batman look her right in the eyes. To her credit, she looked back without flinching.
"I am Princess Celestia," she said, "and I would like to speak with you."
In the back of his mind, Batman figured this would be another situation he'd have to fight his way out of. He wasn't looking forward to it.