Toxin Refinery (Doom 2016)

Toxin Refinery is a classic level from Doom (2016). It is a recreation of Doom's that includes enemies from the later game, but retains the original game's pickup and decoration sprites.

This level is unlocked after finding one of its rooms hidden in the Argent Facility stage. Once unlocked, the full level can be played from the "Classic Maps" tab in the Campaign menu.

Essentials
In this level you start with the pistol, combat shotgun and chainsaw. Open the door in front of you to find a fenced nukage pit guarded by possessed soldiers then turn left and follow the path round to another door, which has a barrel behind it that you can blow up to stagger the soldiers on guard. Head up the steps on your right and push past some imps to another door and go through it to confront another imp and some soldiers, then follow the passage until you round a corner and find an oval-shaped bridge with three soldiers and one imp; do not fall into the nukage on the outside of the walkway as it is inescapable. Cross the bridge and go round the gray tech panel in front of you, watching out for any soldiers waiting to ambush you, then turn left to find a passage leading to a small chamber containing the blue keycard and two more soldiers. When you take the key, an alcove containing two imps will open behind you.

Return to the starting area and go all the way round the nukage pool to a second door with blue jambs that can now be opened. Behind the door are some soldiers and an imp, and there are several more soldiers waiting in the next room that will crowd around the entrance to it and block your way forward. Once the path is clear, head into the next room and walk under the archway to enter a passage with a barrel; a set of stairs will rise and take you up to the exit door which is guarded by an imp. Open a door and kill one more imp, then turn right and press the button in front of you to finish the level.

Other points of interest
Go through the left-hand door in the starting area and head up the steps, then immediately turn left to see another staircase leading down; turn left at the bottom to find a button that will open a wall in the room above. Behind this wall is a tall computer room with imps, soldiers and a pinky who are guarding a yellow keycard. This item is needed to enter secret #5 below.

Secrets

 * 1) Climbing the staircase leading up to the tall computer room mentioned above will lower two walls for a few seconds. The first wall is in the far left corner of the room; step on it before it rises and the computer panel behind it will open revealing a staircase. Follow the stairs down to two imps guarding a pillar, then flip the switch on one side of the pillar to lower a supercharge (actually a mega health).
 * 2) Follow the directions for secret #1, but this time go to the far right corner of the computer room where a second wall has lowered. As before, get on the wall before it rises and the computer panel behind it will open to reveal a rocket launcher guarded by two imps and a soldier.
 * 3) The rocket launcher room mentioned in secret #2 has a nukage river running round it. Follow the nukage clockwise through a small tunnel to find a backpack, a stimpack and a switch.
 * 4) From secret #3, look at the brown wall to the right of the switch to find that it opens; behind the wall is a chaingun and some other supplies. Taking the items will lower an elevator behind them - get on this elevator and a wall above it will open revealing a green armor pickup, as well as a shortcut back to the starting area.
 * 5) There is a misaligned wall on the right-hand side of the room behind the blue door which can be opened. Go through it and turn right to find a staircase leading up to two boxes of shotgun shells and health/armor bonuses. Past these items is a door that requires the yellow key to open (refer to the "Other points of interest" section to find it); go through here to find various items including a megaarmor and a supercharge (the megaarmor is redundant in this version of the level, as the supercharge gives maximum armor automatically).
 * 6) Flipping the switch in secret #3 raises a bridge over the nukage in the starting room. When you cross the bridge the wall ahead will open; follow the corridor behind it until you see a second wall open and reveal a pillared room with soldiers, but do not go inside straight away as a third pair of walls will open to reveal imps, along with a pinky that ambushes you from behind. Past the imps is a passage that led to a secret exit in the original level; in this version, however, the exit switch is removed.