Bursting through the doors of the throne room in Canterlot Twilgiht Sparkle said, "Princess we came as fast as we could."
The we were Twilight Sparkle, Applejack, Rainbow Dash, Rarity, Fluttershy, and Pinkie Pie.
"Good you must wield the Elements of Harmony again to take away the dark powers of Nightmare Moon."
"How did she manage to turn Luna and why is it becoming night time during the day." , Twilight asked rapidly.
"Nightmare Moon was released by me when I told Luna that she wasn't as important as me," Celestia said in a somber voice. "and she is stonger. Strong enough to turn the day to night."
They all gasped from what the princess had said, because Celestia wasn't known for being cruel to her unstable sister.
A loud voice then burst all across Equestria as if broadcast over a loud speaker, "Citizens of Equestria I Nightmare Moon have returned. This is due to your beloved Princess Celestia," then the words that Celestia said to Luna were repeated." but do not blame Luna for it is not her fault she is now safe. Safe with me and now I summon my creatures of darkness."
At Fluttershy's cottage Nightmare Moon blew open the door with large gusts of wind produced by her large wings, speaking in a loud voice that could be over heard the chatter of the woodland creatures Nightmare Moon said, "Discord I free you from this prison."
Releasing a blast of magic Discord was freed; his surpentine body curling out of the door. Proceeding to the heavily armed Crystal Empire Nightmare Moon hovered in mid-air she took aim at the crystal heart that gleamed with magic. Surely, she would have been attacked if not for Discord transforming the creature of the relm to brutality. Nightmare Moon then released a blast of magic that hit the Crystal Heart blowing it away from it shelter and as it hit the floor shattering into a million pieces the crystal began to change to its former grey form. Then as the shards of the heart hit the crystalized floor with a tinkle Nightmare Moon realeased another blast that hit the top stepal of the crystal castle. Then as the darkness hit the top transforming the already graying crystal to an even darker color, loud evil laughs then began to echo through out the empire as a shadowy form began to solidify revealing the revived King Sombra.
"Alright, girls I think from what information I had received from the pegasus ponies, Discord has been freed, King Sombra has been reserected, and we already know that Nightmare Moon has been brought back. As well we have heard the Nigtmare Moon is said to be at the old castle were we first vanquished her.", Twilight finished as chocolate milk hit the window of the train and the finally light of the dull day was extingquished.
The ponies galloped through the Ever Free Forest until all of them slightly flustered except for Rainbow Dash, reached the old derelict castle. They stepped through the thresh hold then small walls of stones began to rise from the floor separating the ponies to leave Applejack and Rarity together, Fluttershy and Pinkie Pie together, Rainbow Dash and Twilight together. raising her voice with magic Twilgiht said, " Alright ladies lets progress to the center and we can meet up there."
Applejack and Rarity may not have gotten along, but it was crusial that they and there element of harmony got to the center with the others. They began to gallop a dark form began to appear in front of them as it became clearer it revealed King Sombra. His horn began to glow releasing a blast of magic that hit the ponies as they attempted to gallop away. The spell that had been cast on the two replayed the worst images that they could imagine stopping them dead still in there tracks.
The center was revealed exposing Pinkie Pie and Fluttershy so did it also reveal Rainbow Dash and Twilight, but no Applejack or Rarity. Pinkie Pie and Fluttershy both walked to the end of the hall that Applejack and Ratiy had been in as they did they stood in front of a dull stain glass window. Closer to the window Discord appeared as if conjured from thin air and with a clap of marionets small strings rapped around Pinkie Pie and Fluttershy restircting the two making them as limp as puppets which Discord controled.
Well thank you if you read this i hope that you all enjoy and that you all have a fun filled pony day
I've got a bunch of stuff to say :
Um, you really should slow down a bit and build up to all of that. Despite the spelling and grammar errors, the initial premise was somewhat believable. That Luna falls again to NMM over repeatedly being ignored and pushed aside isn't entirely implausible, but it breaks up when you consider canon and how contrite Luna was and how forgiving and nice Celestia is. Barring an alternate universe, that plotline has some serious issues.
Still, unless NMM has been plotting in the back of her head, it's hard to see how this whole bit is portrayed as practically instantaneous which both ridiculous and implausible. Not only that, but it's barely believable would just pop out at the last minute solely because of Twilight Sparkle. If you could refine that and give us some other reasons for Luna's sudden reversal (which would help with the plotline problem noted above), perhaps some specific snubbing by ponies that are important to Luna or she's tried to be friendly with? A curfew ordinance in Canterlot for whatever reason that means no one goes out at night (astronomy would definitely not be an option based on that) ?
Also, depending on what you figure the exact events were that lead up to Luna/NMM's initial imprisonment, then Luna should either be feeling guilt over the mess she created because she felt entitled to some things (i.e. was being a bit of a brat, but also truly depressed and lost) or angry with being trapped for 1000 years over trivial things.
If you really want to write a story about NMM returning and taking over, then I would recommend expanding the story to eight chapters at least to give yourself time to work up to it. Fixing your grammar and spelling would be a good start. You could probably split this chapter into three chapters based on the major events that theoretically occur within it (see below).
1) Nightmare Moon's return, her releasing Discord from his prison, flight (as in the past tense of flee or the sense of having left) from Canterlot
2) Appearance in the crystal empire, destroying the crystal heart, freeing Sombra
3) Confrontation with the elements of harmony at the palace of the royal pony sisters, Sombra and Discord present, Celestia cast down
Each of these can themselves be broken down (as seen above) into a couple of separate scenes involving a particular set of ponies.
---
On a side note, the crystal heart is theoretically what keeps the entire Crystal Empire warm, sunny, livable, and free of evil. If Sombra couldn't destroyit , but only hid it then why would NMM be able to just smash it? It really wouldn't make a lot of sense for her to do so in any case, unless it was absolutely necessary to free Sombra. Also, she'd have had to engage in battle with Princess Cadence most likely to be able to get to it.
---
It may be useful to note that in terms of relation to canon this would need to occur after the wedding of Princess Cadence and Shining Armor, but before "Keep Calm and Flutter On" where Fluttershy "reforms" Discord. Discord also seems to prefer subtlety, whereas Sombra goes for the hard hitter approach (both seem to like messing with the characters' heads).
P.S.
I'm a bit lost about the "transfer of minds" bit. Where does any transfer occur?