Mentoring is chaos
Cutie Marks have many meanings, most if not all exclusive to each Pony. Some are easy to recognize, others are more difficult to decipher. Mine is more on the difficult side. Many Ponies don't know what mine is supposed to mean.
A tiara has many possibilities of a meaning. Either that I'm talented in jewelry smithing, I'm not, or that I'm graceful. While that is true, it is not the meaning.
My Mark represents a talent. One difficult to explain.
I can see imperfections. I can recognize if something is fake.
"Diamond Tiara! I need you for something!", yelled my mother.
"I'm coming!", I replied. I walked to her and asked what she needs.
"I need you to bring this book to Twilight's library.", explained my mother, "I'm too busy to bring it back."
Yeah, lazy to dye her mane again. I agreed and left our house.
Getting closer to the library, I got that feeling again.
As soon as Twilight arrived in Ponyville, I saw her Cutie Mark was off. Most days, the small white stars were on slightly different places, the pink main star was shaped weird, even someone without my talent should see it. But no one says anything.
I stepped into her library and gave the book back. I saw that her dragon was cleaning a window, with her owl as "help". Well, the owl flew around. It looked more like him bothering the dragon. He barely kept a grip in a water bucket.
Twilight walked to them and tried to help her assistant, but he dropped the bucket. Twilight managed to stop the bucket with her magic, but the water still spilt over her.
She was wet, so was her mark. It was washed off of her flank. Paint dripping to the ground. But instead of a blank flank or a sand clock, a Mark Ponies have when they are real late bloomers, her Mark was a swirl of purple shades. The swirls moved.
"I had a feeling something was off with your Mark,", I said, "But I did not expect that. I wasn't aware that moving Marks exist!"
Twilight just sighed. "Well, they don't. My mark is odd. And apparently reforming again.", she said, sounding annoyed. But who won't be annoyed when dripping with dirty water. "Considering your Mark, I assume you saw the bad paint jobs?"
"How do you know what my Mark means?", I asked.
"Diamond Tiana, I studied so many Marks to figure out mine, there is hardly any Mark I can't decipher.", explained Twilight. "Now answer my question." She dried herself with her magic. I confirmed with a nod. "I clean this mess, then I explain, okay?"
I nod again, and watched her cleaning Spike's mess.
"I assume no one knows?", I wondered.
"Only the Princesses, and now you.", admitted Twilight, "Not even my family. Follow me into my study, please."
I followed her. She lead me into her more private study. And then a secret room. In there were shelves filled with books, a pin board. On there were many Marks, including the swirls and her 'normal' Mark. All the books in this room were about Cutie Marks.
"Like I said, these moving swirls are not normal. Princess Celestia told me she never saw such a Mark.", explained Twilight. "Especially ones that move or change."
"Change? Isn't that the same as moving?", I asked.
Twilight shook her head. I then saw that the swirls moved. They formed a purple crystal with white stripes around it. It looked like a normal Mark.
"The moving swirls are an inbetween stage. My Mark morphs. Which, again, is not normal, nor that the Princess saw any case like this.", she said, "In fact, to avoid unwanted attention, she told me to keep this a secret. At least until we figure out what is going in. Which means I need you to keep silent about this."
"Of course!" If Princess Celestia wants this, then I have nothing to say.
Twilight smiled relieved. "Good. Do you have any questions?"
"It isn't my business, but did you figure out anything?", I asked.
"Not really. Just that my Mark, at least most of the time, pendles between the same few marks.", she explained. "Most related to magic and other talents I have. Honestly, with each day, I am just more confused about this."
"A real mystery, them... I-I better go.", I said. "Bye? I-I promise I won't tell anyone."
"Good. Have a nice day, Diamond Tiara.", she said, "Stay observant."
... ... ...
It was a well known fact that the Cutie Mark Crusaders tended to cause a lot of chaos and collateral damage when they tried to get their marks. Some ponies are annoyed, others are worried. If they are worried that the trio gets hurt, or anypony who isn't the trio, differs from pony to pony.
None the less many ponies wanted a solution.
So it came that Twilight offered to mentor the three fillies on a regular basis. She will overview them learning new skills in a save and controlled environment.
And if something ends up going wrong, Twilight can fix it.
This system was going well for a few months. Albeit the girls were a bit annoyed that they had a supervisor now. But they soon got used to Twilights mentoring.
But one thing soured the mood. Discord, the least liked Draconiquus in existence – to be fair, he is the only one they know of – was constantly with Twilight. Which included the lessons with the CMC.
But nothing bad had happened – yet – with Discord around. But it sparked a question. Why is Discord hanging out with Twilight and why isn't Twilight annoyed with him? And why isn't Fluttershy complaining?
...
The CMC were, with Twilight's guidance, reading on Cutiegraphy, the studying of Cutie Marks.
"I can't beliebe there is a whole field of research about Cutie Marks!", explaimed Scootaloo, "But why does it exist?"
"To understand them of course.", answered Twilight. She was searching for a few books about said topic. "What they mean, how they appear, what criteria has to be meet for them to form and to represent what they represent. And of course to read them."
"Read them?", asked Sweetie Belle.
"Of course. Take my mark as an example. It is the form of the element of magic.", said Twilight. "A very direct sign to signal magic. Albeit not all Cutie Marks are so on the nose."
"Now, if I think about it, what is Dr Whooves mark supposed to mean?", muttered Apple Bloom.
"His is actually pretty easy.", said Twilight.
"His mark looks like a common hour glass. The filler mark until the real one appears.", replied Scootaloo. "I think he doesn't want to admit he is a late bloomer." Apple Bloom nodded in agreement.
"You never took a close look.", said Twilight. "The waiting hour glass is simple in design. Two brown stripes on top and bottom, connected with two mirroring pale blue triangles." - Twilight showed them a board with a picture of the mark, and a similar looking one with more details. - "Something yellow moving down, no visible sand, though. The Doctor's mark has visible sand particles, pillars on the side of the hour glass and the wood has a slight pattern. They are not the same. Not to mention, his sand doesn't change over the years."
"Why don't we have the waiting hour glasses?"
"You're too young, Apple Bloom.", answered Discord instead of Twilight. He appeared midair. He was followed by winged books. "Delivery, Twily."
"Didn't I ban you from calling me that, Discord?" She bewitched the books, ridding them of their wings. "But thak you for bringing them."
"Command from Celestia, I kinda have to.", replied Discord. He than flew into her kitchen. "Any progress on the project?"
Twilight sighed, "I can't tell you. Not with unclassified ears around."
"Not even a no?", came back. Twilight rolled her eyes.
The three fillies just watched the interaction. They never really saw Twilight talk to Discord so casually. Nor did they think she would let him roam freely in her library, even if it is just the kitchen. From the sounds of it, she is working on something for the Princess, something secret. Yet Discord of all ponies is in the know.
After a while, Scootaloo asked a question. "What do we do next week?"
"We will test if your Mark is related to camping. We'll track to the castle of the two sisters.", explained Twilight. "I admittedly need your help searching the library there for something."
"You want their help yet won't answer my question in their ear shot?", asked Discord, coming out of the kitchen with a giant sandwich. "You're an hypocrite, Twilight."
Once again, she rolled her eyes with her eyes.
"If you won't be such a coward and step into the castle, I won't need to find convoluted ways to squeeze something into my schedule.", snapped Twilight back.
Discord made an offended motion and dropped the sandwich - which was snatched by Spike and Twilight's owl - and teleported to the ceiling. "You know very well that Celestia cursed that place to be inaccessible for me!"
"You don't have to step into it. You just need to care a book shelf worth of books and scrolls!", argued Twilight.
Before Discord could reply, Apple Bloom started to laugh. "Your bickering is so funny!"
Sweetie Belle asked, "Are you sure you can't tell us?"
Twilight shook her head. She then proceeded to kick Discord out of the Library.
She closed the door and turned to the three. "I can't tell you, I'm sorry."
She saw her owl flying around and flying against the shelves, knocking books off.
"What did Discord put onto that sandwich?!", asked Spike.
Twilight sighed.
"We'll help you tidying!", said Sweetie Belle.
"Thanks."
...
While tidying, the three stole glances of Twilights Cutie Mark board. They knew Twilight was studious, everyone knew that. But they had no idea why she was working on this so intensely. She was busy with the library, her friendship studies and her classified project with Discord. How does she have time for this, without neglecting her social life and self care?
After a while Discord came back. He apologized to Twilight and helped tidying. Albeit Twilight was complaining about the order he sorted the books with. Or more so the lack of it. Once again the CMC was watching them argue.
Over the course of their argument, Discord claiming that people who keep order are too lazy to search, Discord wrapped his serperntine body around Twilight like a snake. They watched Twilight trying to free herself. They saw smeared color on Discord's body. Apple Bloom pointed it out. Discord and Twilight took a look.
"Oh, Celestia!", was all Twilight said. Discord blushed and let go. He revealed, where Twilight's mark used to be was purple mist clouds. They looked like her magical aura put purple. It moved. Besides the waiting hour glasses, Cutie Marks don't move. Especially this fast. The clouds were morphing into different shapes.
Twilight walked to them, "I better explain. Please follow me."
Twilight let them into her bed room. She walked to a shelf and opened a secret door. They walked in. The three fillies saw boards like the one Twilight showed them, but bigger, fuller and with more strings connecting stuff. The room was littered with open books. Twilight looked around until she found a book. She took it out of a shelf and opened it.
The CWC saw the book was a picture book childhood pictures of Twilight. At first they were confused why Twilight showed it to them. They then realized why.
"All these pictures... You have different Marks!", realized Sweetie Belle.
"Exactly. You see, my Mark morphs at random. In fact, when I first got it, for the first hour, it switched by the minute." explained Twilight, "This oddity is why I moved to the Palace. The apprenticeship was, to an extent, an excuse to secretly study my mark."
"We never heard of this happening.", mumbled Scootaloo.
"I'm the first and only case the Princess recalls.", said twilight. "There is no cae you could know of."
"Let me guess, the classified project is researching your mark?", asked Apple Bloom. Twilight confirmed with a nod. "Okay, but why does Discord help?"
As if he was called, he teleported in and said, "If there is something out of order, I should know!"
Twilight rolled her eyes.