If you are currently running vanilla Steam version 6.7 or higher, here is why you might want to downgrade to v666 Rev.
The specific version "v666 rev" refers to a particular build or revision of the game, often sought after by the gaming community for various reasons, including: download upd doom eternal deluxe edition v666 rev
Groups like FitGirl, DODI, or Razor1911 have released repacks labeled DOOM.Eternal.Deluxe.Edition.v6.66.Rev.2. These are self-contained. If you are currently running vanilla Steam version 6
How to install a typical v666 Rev repack: including: Groups like FitGirl