During the recently finished online Tails of Equestria (pen & paper RPG) adventure the players paid a visit to a non player character who gave some "subtle hints" of being not exactly eager for visitors. To beginn with, the mare in question was living within a meteor crater in shallow waters off the shore of Trottingham (in the west of the Map of Trottingham I made for the game and visible on the left of the picture Lightbringer, with a magical barrier around it to keep the place from being flooded by the surrounding sea. In legal terms that crater was sort of a state within itself belonging neither to the Equestrian mainland nor to the Griffish isles belonging to Equestria and it had been hinted that a long past attempt of Griffons to interpret the crater as part of their exclave on the island in the south was unsuccessful and may have left some Griffons mentally scarred.
A reason for said scarring can be seen in this animation. The seculded living mare in the crater is named "Maretania" (on the one hoof an alusion to "Mortianna" from the 1991 Kevin Costner Robin Hood movie and on the other hoof aluding to her original homeland Maretonia) by the ponies of Trottingham or referred to as "the crater witch" by some; neither is her real name and finding out about her real name was part of a quest in the game to actually make her a little more cooperative with the players in the group.
In any case she has two abilities one of which is that she is an extremely capable illusionist. What you see in the animation is her attempt to scare the players off by giving herself a terrifying appearance. Her illusionist powers go so far that she could in fact create something along the lines of the Matrix to ponies if she put an effort into it. Her seconde ability (which is a bit of a curse to her) is that she gets some glimpses of the future. The future, according to her, is for the most part something not set in stone but in constant change based on the decisions of ponies. There are however some keypoints in the flow of time which are pretty much unavoidable or which may be harmul but carry the seed of even worse harm if prevented.
In any case "Maretiana" had to leave her homeland because ponies there started seeing her as a fraud because none of the misfortunes she predicted ever happened (those ponies didn't realize that it was because of her predictions and the resulting decisions of ponies said misfortunes were prevented). At one point however she did something that caused her decision to seek seclusion in the crater and avoid most contacts with ponies.
In a fit of anger and jealousy (unrequited love on her part) she not only revealed the coming of Sombra and the downfall of the Crystal Empire to the poor Sir Rich Art of the Sea, but also showed it in very disturbing images to him which pretty much caused his loss of sanity. Maretiana deeply deplored this and was determined never to use her powers again. In more recent years she waned in that determination to some degree and has been using some of her powers in support of Robbing Hooves on behalf of the ponies of Trottingham.