@SYZekrom  
Yeah, they looked like this when NMM first discovered them on the moon – various pastels rather than all grey and cloudy and menacing:  

@Background Pony #ACCB  
Strange, I could’ve sworn I read all of the Fiendships, including Nightmare’s, and I don’t remember that. Then again, I don’t remember anything from Nightmare’s now that I think about it. But at the same time, the Dazzlings’ fiendship have them rap-battle Starswirl alone, which the show has now shown otherwise.

@SYZekrom  
And even if we are, the comics fixed their own canon with NMM’s FIENDship issue (which everyone seems to forget) in which NMM corrupted the Nyx, not the other way around.

i get more of a KH vibe then a Spider-Man vibe, mainly because stygian reminds me of riku

We are the Pony of Shadows!

@Background Pony #EACC  
Well, if we’re not going by comic canon, All Bottled Up shows us negative emotion creates powerful energy, and Friendship is Magic - Part 1 tells us Luna transformed because of the bitterness in her heart. And the energy we see in All Bottled Up is red, just as we see in Princess Twilight Sparkle - Part 1 that Luna’s transformation involved a ball of orange-red energy. So she probably transformed into Nightmare Moon just through immense energy created from negative emotion, like Ganondorf.

The Pony of Shadows really is just like symbiotes such as Venom. He fuses with a pony so that the pony is dominant, but under his influence.
 
One has to wonder if a (weaker) shadow did the same thing with Luna to turn her into Nightmare Moon.

Well there is only one gif I can show