Part 17

Return to the subarena with the glowing green circular symbol. The door will open as you approach.

In the corridor, defeat approximately 6 Unwilling (useful for Weapon Upgrade Challenges like Tactical Scope, Heat Blast, Super Shotgun, Pistol) and 2 Lost Souls.

Turn right and go up stairs to overlook a Mancubus and 2 Revenants. Help them eliminate each other using a Rocket Launch or Gauss Cannon.

Island-hop to the largest platform for shotgun ammo. Turn left to face 2 Cacodaemons; defeat them with the rocket launcher.

Go to the edge where the Cacodaemons appeared and cross the chasm via connecting islands to another dilapidated staircase. You will find small health items, the CODEX ENTRY "Monsters / Mancubus", and Gas.

Defeat 3 Unwilling and a Mancubus guarding another tunnel. You will receive a checkpoint (an auto-save point you restart from on death) (a save point).

Continue up stairs to find 4 more Unwilling near armor.

Find the CODEX ENTRY "Artifacts / Slayer's Testament #3".

Engage approximately 5 Imps fighting 10 Unwilling. This is a good opportunity to work on the Savagery Rune and the Seek and Destroy Rune.

Locate ELITE GUARD 6.4 to the left from where you entered.

Enter a well-stocked tunnel ending with the CODEX ENTRY "UAC Personnel / Olivia Pierce" for a checkpoint before the mission's final fight.

Face unseparated waves of demons: approximately 4 Imps and 3 Hell Razers, then 2 Hell Knights, then 4 Revenants, then 3 Mancubi, and finally 2 Hell Barons and 1 Mancubus.

Save the Quad Powerup for the end. Collect the armor on the top level early on. Keep moving and kill quickly.

Walk up the hill to a holographic replay of a ritual.

Interact with the screen to exit the level.

Pick up the CODEX ENTRY "Monsters / Barons of Hell".

Exit to the outdoor walkway and turn right (left is blocked by fire).

Be surprised by a Cacodaemon on the narrow walkway. You can defeat it with one Gauss Siege Cannon shot with good timing, or dodge its attacks.

At the end of the walkway, turn around and jump up to another walkway. Jump across to a train and follow it to a small landing with two tarp-covered crates.

Behind the crates is a lever for the Original Doom Level. After activating the lever, drop down to another walkway/landing with a grated floor. Turn around to see a large octagonal pillar with a "1" on it. Behind this pillar is SECRET 7.6, "Classic Level / Doom 2: Underhalls".

Immediately upon exiting this area, turn right to see a dirt-floored alcove with crates. Here you will find SECRET 7.4, COLLECTIBLE 7.1, "Cacodaemon Model / Rageguy", armor, and Gas.

Jump your way up to the highest accessible walkway.

You will reach a checkpoint shortly before a long double-jump. Continue until you are looking into a damaged corridor crossing a chasm.

Drop into the hallway through the hole in its roof. Turn around to find ELITE GUARD 7.1, armor, and shotgun ammo.

Go forward to the computer area and find the CODEX ENTRY "Environments / Argent Facility".

Interact with the computer for a 48-second cutscene (a non-interactive cinematic the game plays automatically) (a non-interactive cinematic sequence). You will need a yellow keycard. A marker will guide you to the airlock with an interactable screen.

To the right, face a Hell Razer, a Possessed Engineer, and approximately 6 Possessed. Shoot the barrel to take out many enemies. Expect 2 more Revenants, Imps, Possessed Soldiers, 2 Cacodaemons, and a Hell Knight.

Drop down to a former gore nest location near the Union Aerospace tank. Engage Imps, Hell Razers, and a Hell Knight in an area with fire.

Find a Hologram device near some ammo.

Look down into the next area, which used to have a blue Force Field but now has fires. You will see the glow of a Berserk Powerup. Drop down.

First, face 2 Cacodaemons and 1 Imp. One Cacodaemon can be chainsawed if it starts low.

After that, Imps, approximately 3 Revenants, and a Summoner appear. The Berserk Powerup may outlast the fight.