@Ereiam: Just thought I’d mention it because in Pen Stroke’s and RealityCheck’s sequels to Past Sins, Nyx does have to deal with the stigma of being seen as nothing but an avatar of Nightmare by some people, and she does remember all that’s happened in Past Sins. Nightmare or Nyx (by Past Sins’s author) for instance has Spike giving Nyx grief since during then, he knows what Nyx is, and what she’s done. Becoming mistrustful of her as a result.
 
On a side note, I find Spike’s behavior in Nightmare or Nyx to be another thing in Pen Stroke’s works where a character’s behavior is made harsher by the comics, even though the work predates the comic issues that make said behavior harsher.

@Pepsi_Al  

 
Found the exact quote:  

 
So the truth seems to be somewhere in between actually.

Forgot to address a thing or two myself.
 
@Pepsi_Al  

I forgot to put the word “how” between the words “considering” and “it’s” in the bolded part.
 
Also.
 
@Ereiam  

Actually, IIRC, Luna just takes back the power. Nyx, however, keeps the memories.

@Ereiam  
Erratum #2: “stem from the fact”, not “for”.

@Phantom Rider: Pretty much.

@Pepsi_Al  
So, about half the definition. Mainly she doesn’t have a Rei-type personality at all.

@Ereiam: Well, it was just a random thought that I had. Probably one that came from reading a certain list of traits associated with Rei Ayanami’s expies that was on TV Tropes. As for if she matches anything on said list, and I apologize for the wall of text, well…
 
Love Interest: Nope.
 
Mysterious Waif with a Dark and Troubled Past: I guess this may be subverted. I mean, I guess she counts as a Mysterious Waif. But her life stops being “dark and troubled” sometime after being adopted. Though the darkness and troubles start back up once Past Sins’ equivalent to Manfroy (from FE: Genealogy of the Holy War) puts his plans involving her into motion.
 
Age 10-20: At least, she physically looks to be around Apple Bloom’s age. Don’t know how old that would be though.
 
Pale skin: Negatory. Even if a fur coat would count as skin in this. I would imagine her EQG counterpart would have “ashy-looking” skin, though. Given that Prime Luna has a dark-blue coat, while her own EQG counterpart has powder-blue skin. But that’s another story.
 
Short, usually bobbed hair: Not bobbed. But definitely short.
 
Unnatural hair color, often in cold tones like blue, silver, grey or white (also occasionally pink): Hair color, no. Since purple’s kinda par for the course. A black coat on the other hand, is pretty rare. And understandably, said coat is part of what gives her a resemblance to Nightmare Moon. And it’s what causes Twilight to come up with an enchantment that temporarily alters Nyx’s coat color when the two of them are visiting Cadence in one of Pen Stroke’s own Past Sins sequels.
 
Unnatural eye color, often red, blue or yellow.: I’m pretty sure jade-colored eyes are common among the characters in MLP:FiM. But very rarely does anypony have jade-colored sclera. Or slit pupils for that matter. So far, IIRC, only two types of beings in MLP:FiM have or had slit pupils: dragons, and vessels of Nightmare Moon. (Well, okay. Nightmare ponies in general in the case of the latter. But the only Nightmare ponies we’ve seen in the show or comics, so far, were canonically incarnations of Nightmare Moon.) And Nyx? Well, as anyone who’s read Past Sins would know, she’s more than a vessel of Nightmare Moon.
 
Appears emotionless, quiet or otherwise odd: Emotionless, no. But definitely quiet at least initially. Can’t account for odd, though.
 
A tendency towards talking in Spock Speak: Nope
 
Is not quite human a pony, such as a clone, alien or robot, explaining their odd behavior: I think this may be the hardest to explain. I mean, would a formerly malevolent spirit that was just given a body count towards this? And would said spirit’s new body count as a clone, considering it’s made?
 
Suffers a major injury or illness, or at least is frequently hospitalized: Check on the major injury bit. And it happens toward the end of Past Sins.
 
Occasionally has a strong connection to a parental figure, boss and/or antagonist: Twilight counts Nyx’s parental figure since very early on in Past Sins, and the two do form a pretty strong emotional connection. And Nyx is connected to Nightmare Moon in that, in Past Sins’s context, she’s Nightmare Moon’s reincarnation.
 
Eventually becomes more emotional, such as by Becoming A Real Girl Mare or turning out to have a Sugar and Ice Personality: Over the course of Past Sins, Nyx does become less reserved and shy. So I’d say she counts towards this.
 
But I do agree I could be wrong about this. Like I said. It was a random thought.

@Pepsi_Al  
I don’t really see it, to be honest.  
Nyx’s color palette may be unusual, but it’s the complete opposite of Rei’s. Also Nyx never had Rei’s problems with displaying emotions or making friends.  
Unless you’re talking about their respective origins (Nyx being created from Nightmare Moon, like Rei was created from Lilith), Rei and Nyx don’t have much in common.

Nyx makes an adorable colt! Who knew?

On a bit of a side note, does anyone else think that Nyx could be a bit of a Rei Ayanami expy?

I could see the color scheme making sense in the story, though. Thinking back to NMM’s physical remains, chances are Luna’s DNA may have remained on them, and remained altered. Which could explain the coat color. The hair? I prefer to think that, during the point in that story when Nyx was created, Luna’s DNA wasn’t the only altered pieces of DNA on those remains of NMM. And I’m not referring to Twilight’s DNA either, since it was most likely unaltered at the time.

.

@Background Pony #28C2  
Pen Stroke had the grandfather clause going for him. Any fanfic attempting to pull the same thing again would be considered a ripoff.
 
I think the accusations of Mary Sueness mainly stem for the fact that the story pretty much revolves around Nyx and she’s stealing the show in many scenes (I’m particularly thinking of the tug-of-war where she single-hoofedly pulls a whole team of colts in the mud, the school play where she receives the most applause for her interpretation of Nightmare Moon, and the battle of Ponyville where she deals with most of the monsters of the Everfree all by herself – those scenes have their importance for the plot, but those are the ones where she looks the closest from the cliché of the OP and idolized Mary Sue IMO) and overshadows the rest of the characters who, despite having their part to play in the story, appear like support cast most of the time (Twilight has the most screentime after her, and it’s mostly because of her role as her surrogate mother).
 
Otherwise, I can think of several reasons why she’s not a Mary Sue.  
It is true that she’s quickly accepted by everyone (save for the two token bitches, Diamond Tiara and Silver Spoon), but keep in mind that Ponyville is a pretty friendly community to begin with, that amongst the mane 6, Rainbow Dash is the most lukewarm about her as she thinks of her as a crybaby, and that at the end of the story, there is still a good deal of ponies that haven’t forgiven her for her brief time as Queen Nightmare Moon (then again, aside from Diamond Tiara – and I think Granny Smith in a sequel story –, no names are given).  
Also, a Mary Sue is supposed to be pretty much perfect, which is not Nyx’s case: she has several character flaws which actually work against her. Her nerdishness, shyness and naivety (which some readers have criticized as being written there only to make her more appealing) leave her vulnerable against the two aforementioned bitches, first when they meet for the first time (and she has the Crusaders stand up for her – which itself has become a pretty cliché way of introducing a new character to them in fanfics since then), then when they trick her into going in the Everfree by herself (where she gets in touch with her inner Nightmare Moon for the first time).  
When the ritual is completed and her power restored, her anger at Twilight and Celestia’s “betrayal” mixing up with Nightmare Moon’s own easily convince her to grab the villain ball and keep it for a while. After that, she’s only left with her fan club (the Children of Nightmare), for which she plays the part of the evil queen of Equestria because she thinks it’s the best thing to do at this point (and it takes her a while and several misses to be disabused of this notion).  
Even at the end, after she’s reverted into filly form, she’s left with some anger issues that are implied to have landed her into trouble sometimes.  
Another thing that a Mary Sue lacks is character development, of which Nyx undergoes plenty. Being corrupted by Nightmare Moon’s darkness and being forced to consider whether she should embrace it or reject it have this effect on you, I guess (sure, there’s plenty of angst involved in the process, and if you don’t like angst, you might be tempted to consider it as the usual Mary Sue whinings about being misunderstood and other such nonsense).  
At the end of the story, she’s definitely not the same pony she was at the beginning (and not just because she got her cutie mark): her brief time as Nightmare Moon has left deep marks within her, both from wisdom and guilt.
 
Whoops, look at me going on with the walls of text, even when trying to be as balanced as I can, I can be as annoying as a rabid Nyx fanboy with my logorrhea, sorry about that.
 
TL;DR: Despite having some undeniable Mary Sue traits, Nyx is not as much of one as her detractors make her to be.
 
Love the art as well BTW, I always enjoy some nice character genderswaps.
 
As for WatermelonRat, being a mass uploader, I don’t think he minds our discussion too much, especially with it being as remote from the usual dramafests as can be.

@Ereiam  
Dude, glad you replied and even had a good argument going. It’s rare to find people that actually go their way to not tardrage about Nyx being “BEST OC EVA!!!” nowadays. I can see what you mean though, and even though I disagree, I still see your point.  
As for her being a Mary Sue or her colors being unappealing.. wouldn’t say she looks bad, colorwise. She stands out, sure, but it’s not necessarly bad. Liked the disguise idea too (she looks very plain without).  
Mary sue factor… eeeeh. I think she is liked and accepted way to easily by everyone. (or most. I know there is a part where Celestia doesn’t like her one bit) but the story and the way it’s wrapped around feels far to much like plot convinience in many cases.  
Either way, I think my biggest point is that, at least to me, Nyx is that kind of character that gets away with so much that anyone else would easily be criticised for. Especially being a filly blank slate of an established character with a very basic design that almost 1 to 1 copies the adult design.  
I am actually wondering, if I drew and uploaded a filly blank slate of Celestia, calling her something like.. unno, “Shimmering Hope” and based a story around her and then called her my OC, how many would call me out for it.  
Either way, you make good points.  
Also, sorry artist, for spamming this pic with Nyx discussion. Your art is still pretty swell.

@Background Pony #28C2  
You raise a good point, and I must admit that Nyx is walking a thin line between OC and alternate version of a canon character.  
What ultimately convinces me that she’s her own character though is that she’s pretty much described as such in-story (the conflict about whether she’s Nightmare Moon or not is a fairly important plot point in Past Sins). IIRC Nightmare Moon is basically established in-story as a being born from the darkness in Luna’s heart that went on to possess her body, and the botched ritual that was intended to bring her back to life created an alicorn filly who still carried the potential of Luna’s power and memories within herself (Nyx taps into them several times before they are restored), but was otherwise a completely blank slate – and we see first-hand that Nyx is nothing like Nightmare Moon indeed: even after the ritual is completed, she eventually finds out that Luna’s former inner darkness doesn’t suit with her own identity and eventually goes on to reject and destroy it herself. At the end of the story, not only Luna takes away the power and memories that originally belonged to her (purging her from the last traces of Nightmare Moon beyond her surface appearance), but Nyx gets her own cutie mark, proving once and for all that she’s her own pony with her own destiny.  
The argument about her character design is a bit stronger (after all, with Nyx’s established connection to Nightmare Moon, it would make no sense if she didn’t look any bit like her), but since Nightmare Moon never appeared as a filly in the actual show, one could say that there still was a modicum of creativity involved into the conception of Nyx’s design. Besides, her disguise to go incognito (the hairband, enchanted glasses and vest she’s wearing) changes her physical appearance enough that she doesn’t look like a pint-sized version of Nightmare Moon anymore both in-universe and out.  
Those are my reasons to consider her as an OC. Feel free to disagree with them.  
_{The questions of whether her color scheme of black, purple and turquoise is aesthetically unpleasant or whether she’s a Mary Sue are two different things altogether, but for the record, I’d also say “no” to both.}

@Ereiam  
Not saying that being an OC is a bad thing either, lol. Nyx however is just literally a small version of Nightmare Moon with Lunas S1 hair in purple slapped on. Designwise, I just always thought she was kind of unimaginative. I know what the author was going for, but if I made a baby reincarnated version of any other pony, people would instantly call it out as a rip off.  
And I feel, they’d be right. I could say all I want that her/his personallity isn’t technically the same as the pony I based it off of, but it wouldn’t change the fact that I simply made a canon pony a baby blank slate and called it my own.  
Top it off, with Nyx also somehow being blamed for things she did as Nightmare Moon within the story, which in itself does not make much sense in my eyes. But hay, that’s just my opinion!

@Background Pony #28C2  
Well, Nyx isn’t exactly Nightmare Moon, therefore she’s technically an OC, sorry (not that being an OC is bad…)

Looks more original as colt, lol.  
Still isn’t an oc tho. Nice art however.