The Lost Levels
Taking place an indeterminate amount of time after the Doom marine slayed the Mother Demon in the original campaign, the beginning of the episode finds the marine stranded outside of Hell with none of his weaponry on a distant vacated UAC base. This occurred through the powers of the Mother Demon's sister, known as the Sister Resurrector, who hoped to stop his campaign against Hell by sending him away.
The episode's ending makes reference to the Slayer Testaments of Doom (2016), implying that the journey of the Doom Slayer has begun:
- MAP34: Plant Ops
- MAP35: Evil Sacrifice
- MAP36: Cold Grounds
- MAP37: Wretched Vats
- MAP38: Thy Glory
- MAP39: Final Judgement (Sister Resurrector is boss)
One additional map is included as a "Fun" level accessible from the Features menu.
The Lost Levels can be accessed in a number of ways:
- Defeating the Mother Demon on MAP28: The Absolution in the normal campaign.
- Finishing MAP32: Hectic and then using the "Features" menu's level select option.
- Using any password for MAP01: Staging Area and then using the "Features" menu as above.
- Using a password to access MAP34 directly.
- On the PC version, using the command-line parameter -warp 34
- On the PC version, accessing the kexengine.cfg file in the game's saves directory (found under C:\Users\<username>\Saved Games\Nightdive Studios\DOOM 64 by default) and adding or changing one of two lines in the file: seta g_unlockfeatures "1" or seta g_unlocklostlevels "1". The same commands can also be entered via the console while in-game, but may not take effect immediately depending on what portion of the game is currently active.
Once the episode has been unlocked via methods 1 or 6, it can subsequently be selected using "The Lost Levels" from the episode selection menu, which begins appearing when the g_unlocklostlevels variable is set to 1.