This was a character whose (original) species I made up for a story I wrote. They appear to be vampire bat ponies but are in fact not even physical beings and typically don't even have full autonomy and are more like puppets that do the bidding of "The Magistrate".

I called their species Thestrals (not knowing that some people call bat ponies that lol).

Anyway, Shadow Streak was an anomaly. She had a mind of her own due to reasons. Long story short she was given a physical body, and now she's no longer a thestral but she's also not a vampire bat pony. She's basically undead.

She doesn't need to eat, sleep or breathe, she has literally endless stamina, no heartbeat, doesn't bleed, injuries heal magically after a short while and body parts that come off need only be reattached.