Molestia (sometimes called Princess Molestia) is a fan-created character who closely resembles Princess Celestia. She is an alicorn with a white body, multi-colored mane and tail, and a sun cutie mark. She is usually depicted with a rape face, and occasionally with a dull pink mane and tail.
In the original picture, Molestia was a succubus, but many fan interpretations have Molestia and Celestia being one and the same. Her favorite pastime is molesting ponies and spreading perversity in general. Depictions of her vary from naughty and mischievous to downright sadistic.