How is the humanity corrupted and why does that start apocalypse?
Angra Mainyu is the name of the lord that they followed.
Is there a distructive force that destroy the evil?
Ahura Mazda, one of the good parts sent the fire (his son) to destroy the humanity in the form of a fiery river.
Saoshyant through his rites and ceremonies brings back to life the good and the god of heaven Yima who reigns in this new world of peace... in this new golden age
In what way the world resorted to either its original state or created anew?