Mission 3: Foundry

At the start of this mission, combat rewards are introduced as grey icons in the upper right of your screen. Killing as many demons as possibe will light these up one by one, granting you Weapon Upgrade Points. The idea in the mission is essentially to destroy four different Gore Nests in four relatively separate areas that are all connected by one big main area. Once you've destroyed the four Gore Nests you can enter a large gate, also located in the main area.

Head through the big door to reach the main area of the foundry. Turn left and jump over the gap (try not to fall, because it will mess up the walkthrough directions- if you do fall, explore the main area first and get back to this catwalk). Go through the door to your left (leave the demons in the main area alone for now). In this small room you'll find a Field Drone and a Data Log. Go through the next door and kill the Possessed in this hall, then go through the door on the right. Look to your left to find a panel that requires someone's fingerprints. Check the wall to find a console that recorded what happened to the person with the right hand/fingerprints and follow it (the creature you see is a Hell Knight, which you'll encounter soon enough).

Hop down the broken walkway (you're meant to fall down) and check out the doorway to the right to find an Elite Guard. Head back and climb all the way up. Remember that green lights indicate where you can/should climb up. When you've reached the other side of the destroyed walkway, grab the arm from the corpse and head back to the panel to use it. A door opens, as indicated by a green flashing light. Inside is the first Gore Nest. Destroy it and be prepared to take on various imps and a few new enemies; Hell Razors. These creature attack with large laser beams emerging from their arm. It's best to use the shotgun on them up close.

With the first Gore Nest destroyed, head back the way you came, to the main area of the foundry.

The large gate to the left side is your final destination; you need to destroy the four Gore Nests to get it open. The other door is locked - you need a blue keycard. Continue along the path and ignore (on your right) the long catwalk leading to the right portion of the main area for now. Instead, continue onward and you'll bump into several Imps, Possessed Soldiers and even a Possessed Security. Defeat them, look around for items, then check the body for the yellow keycard.

Before you head back, look at the molten metal to the side of the catwalk here. There's a platform you can jump on, allowing you to collect the Vaultguy collectible. Jump back up when you've gotten it.

As you head back, you'll suddenly be attacked by a few Imps, and no less by a Hell Knight. This towering creature is very powerful and is best defeated by shotgun blasts to its head, or alternatively, if things get really rough, by the chainsaw. After the fight, head down the long corridor in the middle of the main area (now to your left, since you're walking back).

Several Imps appear, alongside Possessed Soldiers. There are various explosive barrels around here, but if things get hectic, simply back out to the long catwalk and use the assault rifle to kill the Imps and Soldiers from a safe distance. In any case, head down the long catwalk and turn left. Walk all the way to the inaccessible door to locate an Argent Cell next to it. It's up to you what you upgrade, but Health should definitely have an upgrade by now. Armor upgrades are less important at this point, unless you are already super good at avoiding damage - which is unlikely.

Classic Doom Map: Nuclear Plant

The lever for this classic map is found on the side of the long catwalk in the middle of the foundry. Move to roughly the middle of the long catwalk and hop to the side, then pull the lever. The portion of this classic map can be found in the area with the explosive barrels and is easy to spot. Clear the entire classic area of monsters, making good use of the explosive barrels (just keep your distance). You can check your map to see if you've explored every portion of the classic area.

When you're done exploring, go back to the foundry and go up the steps on the other side of the area. Be warned, a Hell Knight will appear. Use your shotgun (and perhaps some explosive barrels) to defeat it. If you lost a lot of health/armor, go back to the classic area - there are usually plenty enough goodies around to boost you back up. In any case, these steps (where the Hell Knight appears) lead to the yellow door.

In the next room, head up the steps and look for a Data Log on the desk. In the next manufacturing hall, defeat the enemies that spawn (a few Imps, a Hell Razor and even a Hell Knight). The shotgun works well here. Look for the Prototypeguy collectible in the middle cart on the conveyor belt.

Before going through the door at the end of the manufacturing hall (which leads to the second Gore Nest), look to the stack of crates to the right. You can find a Chainsaw here. Better yet, if you climb the crates you can access a ventilation shaft with an Elite Guard in it. Head to the Gore Nest and defeat all enemies. As you go up the stairs, turn around at some point to spot an AutoMap device on a higher catwalk; climb/hop on and use it. Continue up to find the Blue keycard on a body at the end.

Go down this catwalk and you'll access the blue door area. There's the third Gore Nest down below. Obviously, various enemies spawn again including the usual Hell Knight. Defeat them and use the Health Station if needed, then head back to the main foundry area via one of the blue doors on the ground floor.

Note: There's usually a Hell Knight lurking in the main foundry area at this point. Engage with it if you want to max out your combat rating.

When standing next to the long connecting catwalk, face the direction where you found the yellow keycard and walk a bit in that direction. There's some stairs to the right that you can walk down, which lead to the next and final area (look down below in the main foundry area to already spot the fourth Gore Nest). In any case, go through the doorway on this lower walkway, hop down and shoot a fe Possessed in the orange glowing room down below. Don't go there though, instead move down the steps and collect the Data Log. Climb up and defeat a few more Possessed, then move to the right.

Before dropping down, spot the opening on the left (on the same level as you). If you jump towards the pipes there you can crawl through it to find a Rocket Launcher on the desk. Nice! Be extra careful with this weapon; it's obviously a long-range weapon, although you can upgrade the Praetor Suit so that (explosives from) your own weapons harm you less, which is very useful later on in the game.

Drop down and follow the path to the fourth Gore Nest. Defeat the few enemies here first, then hop over the catwalk (do NOT drop down to your death!) and destroy the next. Clear out the area, then go up to the main foundry area and find the large gate unlocked, finally.

In the area up ahead, activate the cooling turbine and defeat a large amount of demons, including various Hell Razors and Hell Knights. The shotgun is best used throughout the entire fight. When you run out of ammo, switch to the Assault Rifle. Don't worry about your ammo, worry about surviving.

When you've done exactly that - survived - continue through the door at the far other side of the area. You'll bump into another Elite Guard here. Simply follow the linear path now to finish the mission.