Okay, well I just shared my final design for Nyx a little bit ago, but there's a little more going on than me just wanting to draw the girl proper. As a matter of fact, I've been mulling over a story idea for Nyx, a little ambitious on my part. There's a lot of things I've thought should be brought to the table for the character, so I've been brainstorming for over 2 years, and well, here we are.

So what's written hereafter is a plot runabout for the first half of the story, leaving out major spoilers and also a cover image for the story itself. I hope that those of you who read this find the idea interesting, and can wait for me to finish a milestone for a current project of mine to get started on the writing.

Point of References:
Past Sins
Scarred Hearts
Dream-Land
Children of the Night
Alice's Adventure's in Wonderland
Over the Garden Wall

Summery:
“A Nightmare in Eidolon” takes place two years after the events of “Pen Stroke’s Past Sins”, and follows our main character Nyx, who recently suffered an assault from three street thugs during a field trip in Baltimare(Reference to the events of Scarred Hearts). Ever since, Nyx has suffered from dreams involving either herself being attacked, or her family being attacked because of her. In these dreams, she is also visited by a Phantom, a specter of silver mist that visits at every dream’s climax before she wakes. She has trouble sleeping and becomes increasingly agitated in the days leading up to Nightmare Night, constantly having to where her concealment glasses to hide her eyes and the ridicule she gets for them. Parallel to this in an unknown realm, the Phantom watches her along with twelve hooded ponies known as The Order of the Night, planning to find Nyx in the physical world. The Phantom possesses a willing host as a select group of them enters Equestria through a portal.

Dreams continue to haunt Nyx as she prepares for the holidays with her friends, seeking their company to calm her increasing fear of losing her loved ones, which the dreams are feeding. Parallel to these events the Order track down the three thugs in Baltimare and interrogate them to discover Nyx’s hometown. They then kill two of them and frame the third, the Phantom using dark magic to drive him mad.

On Nightmare Night, Nyx and her friends enjoy the festivities, that is until Nyx overhears a pony arguing with her mother, voicing drunken concerns that the filly would be allowed to be free after her two weeks of ruling Equestria as Nightmare Moon(see events of Past Sins). Nyx is also confronted by Diamond Tiara, who, though she’s made up with the CMC, she still holds grudges with Nyx. The two get into an argument, which escalates to that Diamond Tiara points out that the thugs in Baltimare might have been the first to psychically attack her, but they won’t be the last, and that it would be better for her to run away before anyone else hurts her family to get to her. Nyx tearfully runs away, and Applebloom confronts Tiara for using family against her friend, who merely states that, “Nyx needs to grow up and face reality before she really gets hurt.”

The Phantom finally locates Nyx on a hill where she’s run to cry and think about what had been said. However, it does not approach, instead leaving to travel towards Canterlot, and Nyx is discovered by Twilight, who comforts her. In Canterlot, Princess Luna returns to the castle to briefly reapply makeup to her costume before returning to different parties across the kingdom. As she does this, she is confronted by the Phantom, who has taken the form of a small child, crying in a corner. The two talk before the Phantom becomes enraged and attacks her, alerting Princess Celestia, who tries to come to her aid but is prevented by two of the Order’s guards, who unlike the royal guard are able to hold up in a fight. Princess Celestia eventually beats them and enters Luna’s bedchambers to find a large silver mist enveloping her body, which lashes out at Celestia immediately. During the attack she is subjected to a horrific dream of her turning into a monster who uses the sun to create a supernova, destroying the planet before being awakened by one of her guards. The Phantom and the Order escape, and Luna has been drained of the magic she took from Nyx, prompting them both to pay more attention to Ponyville in the future.

Six months pass into the spring, and Nyx no longer suffers from her nightmares regularly, and the Phantom has disappeared. Twilight, with the help of her friends, plan Nyx’s 10th birthday, and the Princesses’ are invited(based on Past Sins this would fall somewhere around the 20th of March). But at the party, the Order of the Night make their move, and the Phantom takes Nyx away into the Realm of Dreams. The Order attempts to escape, but Luna is able to capture one of the hooded ponies, revealed to be Gari.

Nyx awakes in a cave to find that she is in an adult body, and begins to panic, thinking that she has been turned into Nightmare Moon again. However, when she examines herself more closely, she concludes that this isn’t the case since she’s about Twilight’s size and not a full grown alicorn. Upon leaving the cave, she discovers that she is no longer in Equestria. Here we are introduced to the World of Eidolon, a dream-realm of wonder and imagination, a world where mountains hang upside down, the sky is ablaze with fire, and spirits linger. Nyx makes her way through this land and comes across a city, where she conceals herself out of fear of what the ponies there might do to her in her adult form. Traveling the streets she witnesses the work of Eidolon’s people; weaving dreams into tapestries, creating ideas of visions, making puns and light-hearted banter. However, as she gets caught up in the wonder, her disguise falls off, and she becomes exposed to the crowd. To her surprise, however, they respond positively to her, almost enthusiastic.

Nyx is presented to the King, a kind man on the surface with glowing red eyes. She tells him that she was brought to his land by a Silver Phantom. He apologizes to her and states that he knows of the phantom, but it can be a bit eccentric and he really doesn’t know why it brought her to his kingdom. However, he tells her that he can help her return to Equestria if she helps him and his people with a current situation. He tells her that Eidolon is divided by two kingdoms, Somnium(Dream) and Somnum Exterreri(Nightmare), but both were split by the banishment of Luna from that world. Now, Somnum Exterreri is suffering a corruption by a being left behind known as “The Dark”, and its influence is bleeding over to the land of Somnium. But, because she has a connection to Luna, she may be able to remedy the situation. Nyx reluctantly agrees, if not to simply gain her way back home. He then leads her to the border of his kingdom and guides her to the Silva Terrores, the dark forest of Somnum Exterreri. Here she is tested by her magic, her intelligence, her cunning, and her endurance, making a path to the old broken castle of the Nightmare mountain.

This story would explore the concept of fear; how it can consume oneself, how it can be an ally, how one can be manipulated by it. Luna’s fear of being unloved evolved in Nyx to the fear of the ones who have given her love being taken away. What this leads to I won't say for now, but I have thought this story through for over 2 years now, and I'm excited to be working on it at this moment.

6700670
Sounds kinda interesting

6701035
There's more going on behind the scenes than this, but I don't want to get into spoilers. Glad you think it looks interesting at this stage, though!

It is an interesting idea. I'm not familiar with the points of reference nor with Nyx. I kinda know she is a fanon concept of a reborn nightmare moon, but that's it.
So I must admit I'm only mildly interested, I do see a lot of potential

6701055
You really should read Past Sins. Honestly the best story to come from this site, in my opinion