While technically not a level in Doom Eternal, the Fortress of Doom does have its fair share of Modbots, Praetor Suit Tokens, Sentinel Crystals, and other secrets. Most of the collectibles are accessible by having enough Sentinel Batteries to unlock the associated rooms, but some require a bit of exploring to find. The following can be found in the Fortress of Doom:
- 1 Codex Page
- 2 Cheat Codes
- 2 Modbots
- 5 Praetor Suit Tokens
- 3 Sentinel Crystal
All Hidden Collectibles in Doom Eternal Fortress of Doom
Codex Entry: The Fortress of Doom
Look in the Doomguy's personal quarters for Codex Entry: The Fortress of Doom.
Cheat Code: All Runes
You need two Sentinel Batteries to purchase the Original Praetor Suit on the right side exterior of the Fort. Then jump out the window and dash toward the tower into the secret area to get the Cheat Code: All Runes.
Cheat Code: Fully Upgraded Suit
After you complete the Sentinel Prime mission, you basically have to power cycle the Fortress of Doom. You should be in the room past where Dr. Samuel Hayden is staying. Look up and to the right at three glass windows. The center one has a red button. Shoot it to turn on a jump pad. Use the jump pad to get into the vent to get Cheat Code: Fully Upgraded Suit.