Everypony knows there's no such thing as invisible monsters living alongside us. Vinyl Scratch knows better.

After years of seeing things nopony else could, Vinyl discovers that she is a Monster Tamer, a special group of ponies with the inherent ability to see and control the denizens of the invisible Monster World existing alongside the world of ponies, and goes under the instruction of a talking cat who isn't a cat. To keep the peace in and around Ponyville, Vinyl must learn the ins and outs of being a Tamer, and in doing so, ends up fighting everything from chimaeras to giant centipedes. But things might get a bit complicated by the presence of her new roommate, Octavia, whom she has to keep all of this a secret from.

(An MLP / Monster Allergy fusion crossover. If you don't know Monster Allergy, think NBC's Grimm, but as a funny cartoon.)