Carnage - The Last Warforged

Lore:

In the early years of human warfare humans proved less durable than Dwarves, less deft than Elves, and less efficient with arcana than Gnomes. But what they lacked in fighting and magic prowess, they made up for in gold and cunning. Commissioning rare plant fibers from the elves for flexibility, sacred stones, and the best weapons from the Dwarves for stability and balance, pure everore from the Tabaxi, and engineering and ancient incantations from the Gnomes; the humans imbued life where there was none before. Bringing something new and dangerous into the world.
The Warforged was designed to be the perfect weapon, but somewhere along the way it gain sentience. But sentience was too much for the machine, the realization that his creators brought into the world for the purposes of death and destruction was too much for the machine. It decided to bring its creator's wishes to bare on them, it tore through Everhold City leaving carnage in its wake.
Eventually, Humans managed to imprison it in the Pillory of Immortality by sacrificing the entire high table of Everhold City, a target too good for the Warforged to pass up. However, they quickly found this to be a half-measure. As the Pillory ceases aging of entities trapped inside they had only delayed the inevitable, as on a long enough timeline, everything escapes.

Spread

Considered an old wives tale and a bedtime story for children the High Table has a long-standing history of keeping the identity of prisoners locked in the Pillory a secret.  Until this changes there may be no way to tell fact from fiction.

Variations & Mutation

Other variations exist among human cities, the most popular of which is the 'man in the iron suit'. In which a traitor to the Humans was sentenced to wear impossibly heavy iron armor which would keep him alive and healthy but render him immobile forever. 
The man pressed his limbs against the cold iron armor ever day for centuries and after decades had managed to move it a single inch. But in that accomplishment, he found the seeds of his revenge.  Growing stronger every day until the armor was no longer his prison, but his weapon.

Date of First Recording

UE 150