Second Prophecy of Mandos and Dagor Dagorath

Hi,

How you are very expert, well, I have a question:

the Second Prophecy of Mandos and Dagor Dagorath are really discarded?

In 'Silmarillion' (Akallabeth) Ar-Pharazon will be imprisoned in the Caves until the Last Battle. And Fëanor will return and he will break the Silmarils and rekindle the light of the Two Trees.

So... what do we know of the Dagor Dagorath and Second Prophecy of Mandos?


(Sorry, my english is not very good... I'm brazilian girl)

Thank you very very much!