Master Levels offer that next level of challenge, are you up for it? This guide on How To Unlock Master Levels In Doom Eternal explains the concept and execution of the Master Levels feature so you can test your Doom Guy abilities to the very max.
On the Fortress of Doom, Doom Guys base of operations for Doom Eternal, near the main computer, you will see a terminal designated Master Levels. Throughout the game you can interact with this terminal at any point, however there’s not much to do here until you have completed the entire campaign.
How To Unlock Master Levels In Doom Eternal
Master Levels represent some of the end-game content for single player PvE content in Doom Eternal. When you complete the campaign the game introduces you to Master Levels as a further challenge to test your abilities. They are scheduled to change on a regular basis, at the time of writing it’s currently only the first level that is available as a Master Level.
from GamersHeroes http://www.gamersheroes.com/game-guides/how-to-unlock-master-levels-in-doom-eternal/