So.... After trying to draw this and failing miserably here's my idea.... Could you draw Death? She's a bit taller than an Alicorn with white fur, a long, tattered black mane and tail, heavy black lining around the eyes, and her wings are that of a bat pony, just all bone. Her eyes are green with the feline pupils but the whites of her eyes are pure black. She has long, thin black crystal in her left arm and 13 magic runes going down it (no big deal if you can't draw those in) she also has tall black hoof guards
Also worth mentioning she's very slender
There's a reference kinda close