Image imported from derpibooru 
Original Description:
 
Once upon a time, before the land of Equestria was so named, there was a kirin born to one of the multiple wandering tribes of the time. Kirins may have lived in the land long before earth ponies, pegasi, and unicorns founded it as Equestria but no ill will was directed towards either party.
 
This young kirin, the only youth in her herd, would actually find herself as part of the glue that would bind the new nation. Though she would be well into adulthood had she been born a pony, she was only the equivalent of a young filly just barely old enough to have experienced her cute-ceanera when a newly ascended and fresh faced adult Celestia visits her herd. As part of the celestial alicorn’s royal education, she was just supposed to meet with the matriarch of the herd and observe how cultures other than her own can work. The last thing any equine expected was for another alicorn to ascend so soon after the last. [Story coming soon]
 
Though they became sisters in title only later in their lives and facing many differences in personality the prior Earth pony and kirin became inseparable, each filling the gaps the other might have. Her quiet demeanor hid behind it a swirling miasma of thoughts that would examine many branches of thought all at once, something their mentor Starswirl longed to see Celestia grasp. For many moons Equestria flourished under two sets of guiding hooves.
 
The story of Nightmare Moon is much the same as before, a sister feeling isolated from subjects and home alik, lashing out when everything slipped just out of hooves’ reach. A tragic story for a pony, a tragedy for kirin kind. As a former kirin turned alicorn, some ponies theorized darkly that Nightmare Moon was inevitable, simply the remains of her nirek form rearing its dark head. With the growing prejudice against kirins and dwindling population of her sister’ s kin Celestia slowly wiped clean any mention of their kind until even history books and tales told by the hearthside wouldn’t even mention the wielders of wild magic that lived in Eqeustria long before ponykind.
 
Having spent so long on the moon, even with the embrace of the Elements of Harmony, Princess Luna as Nightmare Moon found herself in a constant state of exercising her magic just to remain alive. This strain on her body was not without its own irreversible changes even after the Mane six used the Elements to cleanse her. Her mane and even wings have permanently become a nebulous mass of pure mana, excess constantly dripping off if she doesn’t pay attention. Additionally the areas where Nightmare Moon’s armor rested are permanently stained lighter.
 
As the moon’s phases shift, so too does Luna’s magic. During the full moon she glows with the light of the moon and positively sparkles whilst during the new moon her tail and mane are listless and dull. During an eclipse Luna may struggle to even lift her head.
 
Kirin Headcanon (brief):
 
-Kirins live many years longer than the average pony 200-500 years on average as opposed to a pony’s being comparable to a humans