Jack Friendship, a magic student from AMERICA in Equestria, finds the Elements of Harmony!
Him also being a praised artifact reviewer, he gives the Elements of Harmony a bad review for their limited history and vapid nature, tossing them aside for later.
Hearing this, Princess Celestia comes down to Earth asking why her Elements got such a bad review. Jack reexplains why they were so bad, much to her chagrin.
As punishment for this, Princess Celestia tells Jack he is cursed to use the Elements of Harmony, or risk giving the Elements to another reviewer who might give them a good review.
Jack keeps the Elements, desperate to keep his reputation.
He first uses them to harmonize a monster-of-the-week who had just lost a fight against the mane six and was obviously going to admit defeat anyway.
He then uses it on a school robber who had just realized the err of his ways and was being set free.
Continuing to use this gimmick to get out of actually harmonizing any pony, Princess Celestia becomes angered.
He talks to the princesses, who, as it turns out, are a group of perverted fanfic writers.
They ordain him the Elements of Harmony Mach II and tell him that now he can ruin good plots with it.
He writes in his diary that he, Jack Friendship, started to use the Elements to harmonize evildoers, seeing himself as the only one who can rid the world of chaos and be a god.
Jack sees through the apparent plot changes and engraves his new pony name on the Element of Magic.
This warps reality and separates him from his Equestrian counterpart.
The two begin to compete with each other in an all out war.
Jack stalks his counterpart back to a castle that is actually a wormhole to the world of Tartarus.
Housing the dreaded fanfic writers, he confronts his alter ego and the writers and eventually destroys their insipid plans and restores life to normal.
Now a highly praised artifact reviewer again, he comes under the watch of Royal Detective Gumshoe Sparkle, who takes note of his harmonizing ponies about to reform.
He begins a campaign to hunt down Jack and end his reign of premature harmonizing.
Jack slowly becomes consumed with the power of artifact reviewing, and finds it harder and harder to find ponies about to reform.
To allay this, he attempts to exploit the Elements of Harmony's vague rules and many plot holes.
He tries to harmonize ponies in ways that would make contradictions, like harmonizing someone with a crystal ball that would corrupt them, or harmonizing someone in a comic book or movie, leaving it open that they would obviously go back to evildoing in the next episode/issue, but to no success.
As Detective Sparkle closes in, another artifact reviewer, Iriquois Pliskin, who was the owner of the last Elements of Harmony and had written a review even more cruel than Jack's that never got published, threatens to release it.
Working together to write the ultimate review, they pretend to work with Detective Sparkle to track down the illustrious Elements harmonizer as a clever ruse.
The three go on a wacky side quest, bringing them to the criminal underworld of mobsters called the Italian Stereotype Brothers.
Defeating them, Sparkle is allayed of all suspicion of Iriquois and Jack.
Four years later, Jack is now working for a professional publishing company, and has released a book, The Many Absurdities of the Elements of Harmony.
In doing so, he accidentally rewrites the rules of the Elements of Harmony.
He now has the ability not only to harmonize ponies, but also cause uncomfortably hilarious situations that in no way better the victim, but leave them rightly embarrassed.
This backfires on them, when he fights a clan of gun ninjas desperate to capture the Elements.
One of them shoots him, but luckily, the Elements were in his pocket and absorbed the bullet, thus ruining its ability to cause hilarious situations, and also sending all the ninjas into a funny dance.
At last, Jack retires from his life of reviewing and lives in a happy little home, sitting by his fireplace and smoking a pipe whilst reading the newspaper.
But! A new rival has emerged, bringing Jack out of his peaceful retirement and back into action...
AN INTERNET TROLL!
The troll does a YouTube tirade about how "Gay as shit" and "Fucking lame" My Little Pony: Friendship is Magic is, after finding an illegally pirated video of it on YouTube.
He becomes the next Elements of Harmony holder.
But he only has one Element left.
He attempts to kill Jack, because he had filed a lawsuit, but is stopped, as Jack had legally changed his name to Octopus Agent.
Jack shoots the troll dead, but not before Princess Celestia comes back and takes him to the other world for using the Elements.