On the surface, Doom Eternal is just a high speed, blood-soaked gorefest FPS. When you go a little deeper, its the best high speed, blood-soaked gorefest FPS in years, jumping puzzles aside.
But below that, theres a rich and fascinating array of codices that lay out both the history of hell, a secret history of the rebooted Doom universe, and alien civilizations that mash up magic and hyperscience.
Source: N4G PC Doom Eternals story explained: What we learn from the Codex entries