Seven

I got inspired by Florence and the Machine's 'Seven Devils' song.
This resulted.
The only child of Sunset Shimmer and Sonata Dusk, she was very powerful as a foal. Unicorn (the wings are magic). A strange effect - she was born with her mark on her flank.
Seven's power drew a lot of demons to her like moths to a flame. One eventually took hold of her and made her fire burn brighter. She eventually forgot her real name under its power and simply called herself Seven. Seven serves her demon in whatever plot it wishes. Eventually, she even got her own cult, known as 'Sirens of the Seven'. They're not actually sirens.
Seven and Art (c) Me
My Little Pony (c) Hasbro
Made with DeviantArt muro