On this page of our guide to Doom Eternal we explain how to unlock mission challenges which are based on those known from the previous part of the series. By dealing with these challenges you will be rewarded by the game.
As a reminder, Mission Challenges are additional activities that you can perform during a particular level. Challenges may consist in finding a certain type of collectibles, attacking a group of opponents in a specific way, or destroying a vulnerable spot of the demon's body.
Mission challenges are not available in the first or second level of the campaign. They only appear from mission 3 - Cultist Base. The game will inform you of the fact that the challenges are unlocked as soon as the third stage begins. You can find them in the Challenges -> Mission tab. You can pin every challenge to the main display screen to make sure you don't forget about it.
For more information on how to complete different types of challenges (not just mission challenges), check the Challenges section of our guide.
Each time you complete a mission challenge, a message will appear on the screen.
Completion of all 3 challenges available in a particular mission will grant you a Sentinel Battery.
You can place Sentinel Batteries in the slots available in the Fortress of Doom. This will unlock new rooms in the hub location. In the originally inaccessible areas of the Fortress you may find some various types of collectibles.