Princess Dinky's Letters: A Magical Secret

The letter was written in scruffy handwriting on a scrap piece of paper pulled out of a spiral notebook. Some of the writing hovered above the line, other parts dipped below. It was written by three young fillies who had used a spell to correct their spelling and grammar. Still, it was the most beautifully worded letter that Princess Dinky Hooves had ever read. By the time she had finished, she was moved to tears.

Dear Princess Dinky,

We are writing to you about the letter you sent to us about your past struggles in Equestria, when Tirek and Cosy Glow were in charge. It was a beautiful letter that made us all cry, but we would like to know more about that terrible time.

That letter was torture to read, but it told us so much. We could imagine Tirek and Cosy Glow in charge and you reading Twilight's letter. We all decided after reading it that we needed to know the whole truth to take the burden of hiding this from you. We cannot begin to imagine what it would be like if they were still in charge and we had to live without magic, but we can guess that it would be absolutely horrendous.

We get the feeling that you will refuse. Maybe because you want to protect us, maybe because it's a burden to share something that you did wrong, maybe because the memories are painful. However, we would like to point out that you have already started to share the story, so there is not much point in stopping now. There is so much more that needs to be told - even the gory details - and we want to be able to tell others about what happened in the future.

We hope you understand and write again.
Yours sincerely,
The Cake Twins and Lily Waterfall

Dinky was torn. She started pacing in her bedroom. After reading that, she really, really, really wanted to tell them, but their mental well-being could be severely affected if she did. It was Twilight who had persuaded her to write the first letter: she had been talking about what a burden it was to carry the secret and how foolish she was to cast the Carrying Curse, which meant that they could not speak about what had happened to them, unless they had already been told, except through writing. And Twilight was correct in a way because it was a burden to not be able to talk about it. The fillies had also been pestering her. She had thought the first letter would deter them. Apparently not. Ugh. Twilight was so much better at this. She could make an almost instant decision on what to do. She was so good at being a princess. A bit like when Celestia and Luna had been in charge. They were all so good at their roles. Dinky herself was still having trouble being a princess, even after all these years. It seemed that she would need Twilight's input to make a decision.

She used magic to teleport to Twilight's palace, and knocked on the front door. Twilight herself answered.
"Dinky!" she cried. "Come in, come in. I've not seen you in ages! How are you?"
Dinky walked to Twilight's side and replied, "I'm good, but I have a dilemma."
"What is it?"
"It's about-" Dinky began and she tried to speak but her lips got stuck together and no sound could leave her mouth. Her eye Drs darted to the guard at the door. Twilight saw and understood what Dinky meant. Carrying Curse. Past lives under Tirek's rule.
"That's okay," said Twilight, "we'll go to my chambers."

They walked up three flights of stairs and shared small talk. Eventually they reached Twilight's bedroom. A guard stood there.
"I need to talk to Princess Dinky in private," Twilight told him. "I will need to cast a sound seal. If somepony wants to talk to me, or you just want to check on me, knock three times." The guard nodded, the two mares entered Twilight's bedroom and Dinky closed the door. She cast the spell and Twilight said, "It's about the fillies, isn't it."

It was a statement, not a question. Twilight already knew why her fellow princess was here. Dinky squinted, and then she was thinking Twilight's thoughts.
Dinky doesn't know what she's doing. She's telling foals. She will scare them and they'll leave those letters out and then everyone will know that I...
Dinky yelled in pain as a sudden headache overcame her. It felt like she had spines in her head. She would have called for help, but she had cast the stupid sound seal so the guards wouldn't hear.
"Twilight, what was that?" Dinky asked, her head throbbing.
"I thought I told you not to go rooting around in my head. I have things I don't want other ponies to know. I my friends found out, they would turn me into a statue for all eternity, like Cosy Glow and Tirek and Chrysalis."
"Tell me. I can hold my tounge. Or have you cast another of those Coward Carrying Curses so that you can't embarrass yourself?!" Dinky shouted angrily. Twilight was more worried about herself than her subjects and the next generation of ponies and sharing the truth to make sure this never happened again.
"Dinky, you were cleared of all crimes. I wasn't given that luxury. I had to serve a prison sentence without magic for five years. I wasn't allowed to leave my shoebox of a room in all that time. I didn't even have a window. I didn't even get to see the sun in five years."
"I could clear your name. And who says I'm going to tell everypony whatever you did? What was it, by the way?"
Twilight mumbled something.
"Can't hear you Twilight!"
"I am the shadow."
"That means nothing to me."
"I am the Shadow Pony."
"In what way?"
To answer, Twilight conjured a mannequin that looked exactly like her. She then used her magic to create shadows that curled around the mannequin and formed armour that was such a deep purple it was almost black. The mannequin's irises began to glow red, and the pupils shrank to slits. An exact replica of the Shadow Pony who had done unspeakable things in the rebellion that led to Equestria's freedom.
Dinky was lost for words. "You - you don't mean-"
"Yes. That was me."

Dinky teleported back to Canterlot and decided she needed to tell the whole tale. Including the fact that her friend, mentor and fellow princess was a murderer. The Shadow Pony.