She is a pony that represents the dead (but she isn’t actually dead). She is a demon pony, but she’s actually rather kind and friendly, despite her status and appearance. She also often appears to ponies who have recently experienced the death of someone they know, and tries to help them gain closure and help those ponies move on.
She is fond of Nightmare Night and the Day of the Dead, as she likes seeing all the spooky things that happen during the day. She also likes to party, and the skeleton pattern on her body can actually light up and glow in the dark.