In a secure room in the centre of Canterlot Castle, Princess Celestia herself stared at the creature that most ponies thought to just be a figment of fantasy. It had a short, jagged horn, a smooth black chitin exoskeleton, what looked like holes in it's legs, and green dragonfly wings. "Even Canterlot Intelligence, whilst it does know that Changelings exist ever since a few were caught in Baltimare, does not know much about you other then the myths-and yet you have decided to defect from your Hive and tell all. What are you expecting to gain from this? Why would you turn traitor against your own kind? And how do I know that this is not some sort of trap? Maybe you are a double agent who has only pretended to defect so that you can spy on my little ponies or worse."
"What I would like? A place in witness protection with all necessary documents and a job with the weather ponies in Cloudsdale. As for my disguise, I can do that myself. There is no need to perform any surgery on me. Given that I doubt you know what my insides are like, that is just as well."
"As a captain in Queen Chrysalis's army, normally defection would be unthinkable. But Queen Chrysalis is planning another giant love raid on Canterlot, with much more sneakiness this time-something that really goes against the Changeling Way. In a place like Ponyville or the smaller towns and villages, you ponies leak love and we just have to walk around with our emotion sacs open and gather it up. In the big cities, we have to either work to get it or steal it. There are other Hives out there with a very strong interest in staying in the shadows and maintaining the Masquerade, and if Chrysalis ruins it for everyling, love will become far harder to gather and the other Hives may well attack our own. As it is, she caused serious trouble for everyling. Changeling warfare is quick and ruthless; it has to be as we lack the love reserves for long drawn out wars."
Other the next few hours, the changeling told the Princess all sorts of information. There were no less then five major Hives, and they shared control of the great cities. Only one Hive looked like some great insect nest from the outside; the others had well concealed castles. Replacing ponies was rare, but it did happen, and there were a few changeling spies in the Royal Guards, the government, and even one in Canterlot Intelligence. He had heard that an attack was planned on Canterlot during the Royal Wedding, but at his level he did not know the full details which were only known by the Queen and a few of her generals. When he had told her everything he knew about the planned attack and his own race, he said "Oh, one more thing-Diamond Tiara is innocent! She was smirking at her trial because she knew that she didn't murder Apple Bloom and trusted the Equestrian legal system to find out the truth."
"So if Diamond Tiara did not kill Apple Bloom, was it a changeling that did it?"
"It was only meant to be a replacement, with her cocooned so a changeling could take her place, but something went wrong and she was killed outright. Panicking, the changeling took Diamond's shape just before other ponies showed up and went on the run. The guards arrested the real Diamond, and as she and Apple Bloom hated each other, she clearly had a motive to kill Apple Bloom."
"You can stay here tonight and tomorrow you can talk with the Witsec ponies and get a new ID sorted out to hide from your fellow changelings. Diamond Tiara cannot be declared innocent yet or Queen Chrysalis might find out that something is up. I will put the Royal Guards on alert and put a magical shield around Canterlot to keep the changeling army out on the day of the Wedding."
*****
"Wake up, Sis!" Applejack woke up her *sister* with a gentle shake and a forehead kiss. Diamond Tiara liked forehead kisses but only from her father but she knew she had to play her part like she always did. "You're going to be a bridesmaid! At the royal wedding no less!"
Diamond bounced out of bed with a big smile on her face that she didn't really feel. "Yay! Cutie Mark Crusaders bridesmaids!" It turned out that she genuinely enjoyed being all dressed up. It had been a very long time since she had last been allowed to wear a pretty dress at all or indeed any clothes but her ribbon in her hair. Of course most ponies went around naked most of the time anyway but she still missed her fine clothes and her diamond-studded tiara. The other two Crusaders admired the fact that she had her cutie mark now and got on very well with her, although she always sensed tension beneath the surface when she was with them. After having to act like Apple Bloom for so long, she knew perfectly how she had to behave with them.
Soon enough she and the other two Cutie Mark Crusaders went on the train to Canterlot. As they passed through the force field and past the many spear-armed Royal Guards, she wondered what the problem was to have so much security around.