My Fallout: Equestria AU Idea

This takes place sometime during the events of Fallout Equestria.

Ever since the Last Day struck, it devastated all of Equestria and most life formerly occupying it. Other life mutated into hostile, fearsome creatures. But a barren, isolated portion of what is now known as the Equestrian Wasteland far East of the Celestial Sea, has been devastated, perhaps the most during the war and the dropping of megaspells. Hereby dubbed 'The Rotten Wastes' by many brave souls due to the ever looming faint smell of dead flesh and corpses tainting the irradiated air, even if there's no carcasses to be seen. Very few ponies; no matter if they're New Canterlot Republic or Steel Rangers, Grand Pegasus Enclave, Raiders, or mere High Class Field Researchers don't dare to enter the zone, in fear of the dense and unyielding ashen mist and foul aroma of the dead that is said to drive the most sane and hardened of ponies to insanity if exposed to it for too long; either driving them to crazed, ghoulish cannibalism or deforming their bodies into eldritch horrors, or what the brave denizens who decided to house themselves in the intoxicating wastes called 'The Rotted'.

Those who wish take the task of venturing to the rotted landscape are required to traverse via riverboat located on the East coast of Fillydelphia near Horseshoe Bay, as the bridge to the land has been destroyed during the megaspells, and are to wear special 'Purifier' gas masks; masks that were mass produced by an nameless industry for the once thriving land, 'Purifier' gas masks are enhanced with magical properties to resist and endure the intoxicating ashen mist, or any harmful gas for that matter, in order to even survive a day out there. Those who do not, have mere minutes before their mind is decayed and hellish insanity and deformation takes over. But even with this all this information to survive out there, most survivalists residing within The Rotten Wastes would heavily advise you to keep away from the crater located at the heart of the Rotten Wastes; it is said that the Undead Dragon that caused all this destruction and deadly mist resides in the center, where one of the megaspells first struck.

The undead dragon, whose name is practically illegible to nopony but an experienced Scribe, is believed to be from the eldest times of Pre-War Equestria, said to occupy the very land that is now its resting place. However, when the Last Day came and a megaspell out of the three that was sent by the Zebras in an attempt to kill the beast for the sake of religious beliefs, the dragon instead absorbed the explosion and released it as the dangerous mist, killing or infecting those who weren't already killed by the massive magical nuke, killing itself in the process. Now with over two hundred years of decay after the havoc, the dragon now quietly slumbers as an immortal, immovable, undead beast, capable of destroying or even spreading mass devastation once more if awoken, potentially destroying the current land it inhabits or worse; spreading its mists of mass destruction to the mainland.