Unicorns have horns to use magic.
Pegasi have wings to fly.
Earth ponies have... what?

Ponyville is a rustic, old town established by the hardworking and rather normal Earth ponies. But even now in modern times there is often tension between the three pony types living there. Strange events are beginning to happen and Twilight Sparkle takes it upon herself to find out what is wrong.

If there was a mystery category, I would add it. It probably won't have enough dark content to be categorized as "dark" (and so it's still rated everyone if I can restrain myself from going overboard).

The story image source is here. If it was originally by someone else then I would love to know who.