Nightmare Nyx (Interdimensional Friendship) by @Videogamejunkie443 (Matthew Alchtiwi)

Of course, Nyx will appear in my project because the Past Sins universe is pretty much the OG MLP AU.

She will be from an alternate version of the Past Sins universe. In This AU, Princess Luna accidentally left a little bit of Nightmare Moon's power inside Nyx. She built up that power and planned to become a hero like her mother and use it for good one day, and from when you first see Nightmare Nyx in Interdimensional Friendship onwards, she will.

The original image is in the description of this Deviation: https://www.deviantart.com/90sigma/art/Nightmare-Moon-303863311

Cutie Mark art by AlexLayer: https://www.deviantart.com/alexlayer/art/Cutie-Mark-Nyx-258674977

Past Sins & Nyx belong to Pen Stroke https://www.deviantart.com/penstrokepony

My Little Pony: Friendship is Magic belongs to Hasbro and Lauren Faust: https://www.deviantart.com/fyre-flye