Board Thread:Lore Discussion/@comment-7629073-20130402085627/@comment-33206573-20190816163509

This is my own theory:

Whenever Nirn is in a great time of need and is facing a large threat(e.g Alduin or Mehrunes Dagon), there exists some sort of supernatural force or energy, be it of Aedric origin or otherwise, as a contingency for these types of situations. We'll cal it "the hero force" for the sake of this theory.

In these times of need, The Hero Force bonds to a mortal being that is considered "worthy" of being a hero. Great gifts are bestowed unto them during these brief periods, which explains how they always become so powerful so quickly. But once The Hero fufills their destiny and their prophecy is complete, the Hero Force leaves them and transfers to another host. It basically has a similar function to dragon souls in Skyrim. This could explain how multiple TES heroes are alive at the same time but are still, in a sense, "reincarnated" from previous heroes.

But of course this is all just headcanon and I have no evidence to really support any of this.