This is Sparkfree, one of Celestia’s personal aides. In short, she was given to Celestia as a hatchling by a “friend” and was taken under her wing as an apprentice. Today, Sparkfree serves as one of Celestia’s most powerful fighters, and is unmatched in her loyalty throughout the Royal Guard.
 
To bring her closer to her pony subjects, Celestia put Sparkfree through something similar to the Alicorn Ascension spell, making Sparkfree a hybrid between pony and changeling. Unfourtunately, all this did was confirm Sparkfree’s opinion that she was “higher up” than everyone else.
 

 
There’s a lot more to Sparkfree’s story and character than that, but I’m just not sure how to present her to people for the first time. She’s easily one of my stranger OCs.