Doom Episode 1 Walkthrough

The genesis of Doom places the character at the entrance of a small hangar, part of a Union Aerospace Corporation research and waste disposal facility located on the terraformed Martian moon of Phobos (Tei Tenga in alpha development). The military have used the UAC facilities to conduct secret experiments in interdimensional travel. Strange occurrences have been happening, suggesting that the interdimensional portals have been intercepted by forces of Hell. One day a panicked distress call comes from Phobos, and Mars' other moon, Deimos, completely disappears from the sky. You're sent to the UAC base to investigate...only to discover that you're the only human there that's still alive.

This walkthrough is focused on the objective of exploring all areas. Throughout the page, ▶ points to "official" secrets counted in the end-of-level tally, and ▶ points to other hidden areas.

E1M1: Hangar

Bear left at the entrance, and ascend the stairs to a small platform surrounded by windows, where a piece of armour awaits. Go back to the foot of the stairs. ▶ On the outer face of the left column, there is a switch that controls a hidden door opening out into the central courtyard (Doom 1.9 Ultimate only). Otherwise, bear left at the sunken area and follow the passage into a computer room, where you'll meet your first zombified enemy. Continue on to a room with a zigzag walkway over toxic waste, and note the platform at back left...you'll go back there again. 1 ▶ Continue on to the corridor that follows, and notice a discoloured panel on the right wall. This is a secret door that leads to the courtyard you saw earlier. Backtrack to the corridor, and enter the dark room with lattices. You'll hear a faint sound of machinery whirring. 2 ▶ Go back to the zigzag room, and you'll see that the platform you saw earlier has lowered, allowing access to a room with items. 3 ▶ Go back to the zigzag room (again), cross the shadow line that separates it from the computer room, and run back to the hidden area you had just come from. A hidden lift in the corner has lowered, allowing access to a hidden platform with armour bonuses (Doom 1.2 and later only). Follow the corridor back to the dark room with the lattices, and take the exit.

"Hangar" was designed by John Romero, and reflects his approach of devising realistic, yet chaotic levels with winding passages and irregular footprints. Since this level would be every player's introductory experience with Doom, it was conceived very carefully, and was one of the last levels to be finalized in the game. Although no versions of the map exist in the pre-release alphas, video footage exists of development from November 1993 (one month before the game was finished). In this prototypical version of the map, the platform left of the entrance is obscured by a hidden door, and the room at the north end is completely different.

Gallery

December 1993 map from the initial shareware release, lacking west and north access to the central courtyard or the hidden platform over the "zigzag room."

The memorable "zigzag room" of E1M1.

"Hangar," as depicted on the intermission screen. The illustration resembles a hangar more closely than the actual level does!

E1M2: Nuclear Plant

You begin in a large lobby area, opposite a central control "island" accessed up three steps. Enter the "island" and go through the opening at left, where you'll find a lift leading to a shotgun. Return to the lobby. Take note of the alcove on the back wall, with armour: This connected to a corridor on alpha versions, although it dead-ends on the final map. 1 ▶ On the outer east wall of the "island," there is a discoloured panel. This is a secret door that leads to a dimly-lit area with a switch. Hit the switch.

The east side of the lobby has two doors that open up into a U-shaped staircase, leading to a windowed area and a large alcove where you'll find the [Red key] red key. 2 ▶ The switch that you touched earlier has opened a door on one of the landings, leading outdoors. Go out, and you'll find a soul sphere and chaingun.

Go back to the lobby. ▶ In the southwest corner (left of where you started), there is a lift leading to some hidden items. Now proceed through the [Red door] red door. You'll arrive at a fork. Bear right, and enter a room of toxic waste. The pillar in the centre has a switch on it. Hit the switch, and return to the fork in the corridor. A door has opened on the opposite wall, dropping down into a dark maze. 3 ▶ Follow the maze to the eastmost wall, and look for a panel flanked by stainless steel columns: This is a hidden door leading to a room with a backpack. 4 ▶ Now work your way to the westmost section with pulsating red ceiling lights. Shoot the central portion of the wall (you may do this by accident, shooting the imp that spawns in front of it), and a door to a secret passage and staircase opens. 5 ▶ On the third staircase landing, stop, turn right, and open a hidden door with armour bonuses within. Continue up the stairs to a room with big windows and a chainsaw on a pedestal. ▶ To lower the pedestal and get the chainsaw, look for an inconspicuous switch in the left rear corner of the room.

Retrace your steps through the maze (you may poke around and look for items and enemies, if you like), and return to the corridor. Take the left fork, and follow your way up an L-shaped staircase. ▶ Just before you reach the top, look for a small alcove to the left. Enter it. This will drop down into an observation area overlooking the chainsaw room, with a medikit.

Take the lift back up. The top of the stairs opens into a room with a winding walkway over toxic waste. Interestingly, the October 1993 pre-beta contained a winding passage forcing the player to wade through the waste, taking hit damage...which explains why there are so many medikits on the opposite landing. 6 ▶ On that landing, look for a discoloured panel on the left side. This hidden door leads to a balcony with health and armour bonuses. Drop down into the dark, spooky room below. A switch is located on the wall opposite the lift. Two doors will open, leading you to the exit.

"Nuclear Plant" was a pivotal level in Doom's development, since this map was both John Romero's first to near completion and the first to make extensive use of features such as staircases, high ceilings, and non-orthogonal walls. Early versions of the map were featured in alpha versions and pre-release screenshots as early as February 1993.

Gallery

February 1993 alpha map, revealing a rough layout with numerous differences from the final version. The maze in the southwest corner is highly irregular, and the east platform and north exit area had yet to be added at all.

April 1993 alpha map, fleshed out with the addition of the east platform and hidden chainsaw area. No outdoor areas exist, and a winding passageway extends north from the central lobby. The May 1993 version is practically identical.

Detail from May 1993 intermission screen, showing the level as a diminutive "power plant."

October 1993 pre-beta map. Although closer to the final form, this version of the level retains many differences: The elevated area on the east side is much more condensed; a winding passageway through toxic waste appears in an area that was later changed to an open room, lifts are used in places where stairs were later present, and two secret rooms are missing.

The soul sphere and chainsaw both make their first appearance in this level...although neither are easy to get to!

Another iconic room, with a pair of switch-operated doors leading to the exit. This room figured prominently in alpha development, and represented John Romero's first foray into high ceilings and mezzanines.

"Nuclear Plant," as depicted on the intermission screen in the final game.

E1M3: Toxin Refinery

You begin in a small, interstitial room. Go through the door to a larger room with a loop-shaped platform flanking a pool of toxic waste. Bear left, and enter the next door. It leads to a triangular room with windows overlooking a soul sphere and a switch. Take the staircase up. ▶ The first alcove on the right contains a panel that opens to reveal an inaccessible interior area. Continue following the corridor until it leads to an outdoor area with a split walkway straddling yet another waste pool. This is followed by an indoor area, with a few enemies and an illuminated platform for the [Blue key] blue key.

If you have an inkling that this looks like a trap, you'd be right: The lights will go out, and a horde of imps will break out from a hidden room. Fight your way back outside, and ▶ jump into the central pool: There's a medikit down there, as well as a switch that drains the pool and raises the platform. (On Doom 1.0 shareware, this is controlled by a walkover trigger and a switch on the north wall.) Follow the corridor back the way you came. Just before you reach the triangular room, you'll see a separate set of stairs dropping down to a dark room on the right. Go this way, turn left at the bottom, and hit the switch on the wall.

There's a lift accessible from this room. First, however, return to the triangular room. A passage has opened in the space between the two windows, leading to a computer room. As you go up the stairs, you should hear a lift move in the distance. 1 ▶ Bear left and RUN to the far recess on the left wall, which has dropped to floor level. A passageway will open up, leading to the room with the soul sphere. To lower the pillar, operate the switch at its base.

Backtrack to the computer room and ▶ pick up the [Yellow key] yellow key, which is hiding in the middle. Leave the room, then re-enter so that you hit the lift trigger on the stairs again. 2 ▶ Bear right and RUN to the rightmost recess on the back wall, which reveals a dropped platform and passageway much like the last. This one leads to a room with a rocket launcher and a stream of toxic waste. 3 ▶ Follow the right branch of the stream out of the room to a brown platform with a switch. Hit the switch to trigger a platform elsewhere in the level leading to a secret exit. ▶ Then, look to the right for a discoloured panel hiding a door. This leads to a series of lifts, taking you back to the dark room you were in earlier.

Go back to the room with the loop-shaped platform you saw at the start of the level. You'll notice that a platform has risen in the middle of the pool. First, though, go through the [Blue door] blue door on the opposite side. It opens into a slimy room with a forked walkway. Follow the right fork, then stop just before you enter the passageway. 4 ▶ The wall to the right is a hidden door leading to a room with health bonuses. Go up the stairs to find a chainsaw, then a [yellow door] yellow door leading to a ton of goodies.

Return to the room with the forked walkway, and continue down the passage to a dark room containing the exit portal. A staircase will rise in the middle.

Secret exit

If you'd like to take the secret level, however, it's time to skedaddle back the way you came. Return to the room with the loop-shaped platform at the start of the level, and walk out onto the platform in the middle. 5 ▶ As you approach the back wall, a passageway will open leading to the inaccessible interior area you saw earlier. Be alert: Several walls will open up and enemies will ambush you, including your first pink demon in the game. Once you've gotten through that, follow the passageway in the back to the secret exit. Don't hit the switch just yet, though! 6 ▶ The left wall is a hidden lift taking you to a ledge that overlooks the outdoor area, with a box of rockets for the taking.

The secret exit appears to have originally been intended as the sole exit for this map, with the "main" exit not added in development until after May 1993.

The yellow key is not necessary to complete this level of the game.

Gallery

May 1993 alpha map, lacking many of the areas found on the east side of the final version. This level does not appear on the May alpha's intermission map nor in the April 1993 alpha, although circumstantial evidence suggests it took the place of the observatory in early development.

The rocket launcher makes its first appearance in this level.

A well-hidden cache of bonus items, accessible with the yellow key.

"Toxin Refinery" is depicted on the intermission screen with a circular footprint having no relation to the actual map.

E1M9: Military Base

Congratulations: You've found your first secret level! The Military Base consists of eight rooms connected by staircases to a central, elevated courtyard.

You begin in an alcove that opens into the courtyard itself. Kill the enemies in the central cage, then take the west passage (on the same side you started on) to a lower room with an open skylight. Pick up the [Yellow key] yellow key behind the lattice. The staircase at left leads to a locked red door, while the staircase at right leads to a Hell-corrupted room with a pulsating pentagram. Enter this room to get a rocket launcher...and a horde of teleporting monsters.

Return to the central courtyard and proceed straight ahead to the east passage, which leads into a room with a lift on the back wall. Step onto the lift, and be lowered into an open-air room with three pillars in a pool of toxic waste. ▶ A ledge on the left edge of the pool contains several bonus items, plus a trigger that lowers the pillars. Take the lift back up to the previous room, and bear towards the far left corner: 1 ▶ You'll find a hidden lift that takes you to a toxic waste pool, with a chaingun and bonus items. (Stepping onto the central island is necessary to register the secret.)

Go back to the previous room (again), turn right, take the staircase down, and enter the [yellow door] yellow door. Inside, you'll find the [red key] red key. Continue through the yellow door on the opposite side, which leads up to a room with four torches around a central obstruction. ▶ A hidden lift in the near right (northeast) corner connects back to the toxic waste pool you saw earlier. A staircase on the opposite wall leads down to the [Red door] red door. Enter this room, enter the hidden alcove in the far left corner, and hit the switch. A hidden passage will open, leading back to the torch room you were in earlier: The central obstruction is now gone, revealing the [blue key] blue key.

You're almost finished! Return to the central courtyard, proceed straight ahead to the north passage, and go through the [blue door] blue door. You'll find yourself in a room split by a chasm, fighting your first invisible demons (spectres). 2 ▶ Open the discoloured panel on the right wall to reveal a hidden storage area with weapons sitting atop pillars. A lift on the far wall allows you to collect the weapons by running from pillar to pillar, but doing this might be easier said then done.

Drop into the chasm in the previous room, and follow the toxic river to a platform with a switch. Hit the switch, then turn around: An escape door has been triggered (along with a hidden door releasing more enemies into the previous room). This leads to a lift and door, bringing you back to where you were before. A bridge has risen, allowing access to the exit switch.

Gallery

E1M9 is the first level in which the player encounters a Hell-corrupted room with teleporting enemies.

"Military Base" as depicted on the intermission screen, in the far corner.

E1M4: Command Control

"Command Control" was one of two Episode 1 maps devised by Tom Hall, and is characterized by its dense layout and non-linearity. Early versions of this level seen in alpha development were also hyper-realistic, featuring locker and shower areas for UAC staff. These elements were later de-emphasized from the game, and following Hall's departure from Id in August 1993 the level was tweaked by John Romero to impart a darker ambience.

You begin in a small vestibule. 1 ▶ A hidden door on the left wall will reveal a medikit and backpack. Go through the door straight ahead to the open-air lobby. You may choose to go in any direction. For the purposes of our walkthrough, however, let's follow the central entrance to the vestibule panelled in hexagonal tiles. Hit the switch (if desired), and ride the lift to one of the two observation areas. Turning right will place you in a large circular room with a central area bounded by four doors. Simply approaching the doors is enough to open them. Watch out for imps, and retrieve the [blue key] blue key.

From here, you can explore some of the other areas. The north passage leads to the other observation platform, followed by an open hall with an overhead gallery (replacing the locker room in the level's earliest incarnation). At the far end of the room, you'll find a lift that enables access to the gallery. ▶ Entering the gallery will trigger a hidden door, revealing a room with health and armour bonuses. ⚠ But be careful up there: The lift only works once.

Opposite the gallery, you'll see a passageway leading back out to the lobby. Walk this way, then duck past the "Poison" signs through the entrance at the far end. This takes you to a room bisected by a chasm and toxic river. Go up the staircase, and fetch a radiation shielding suit from the circular room: You'll need it, because you're going to jump in the river! 2 ▶ Going left will take you to a hidden platform with bonuses, and 3 ▶ a soul sphere. ⚠ Be careful when getting the sphere: You'll need to flip the switch, then run onto a lift that only works once. ▶ Meanwhile, going right will lead you to a lift and platform overlooking the staircase you were on earlier, leading back to the circular room.

Now it's time to explore the west passage. Turning right will take you to a room overlooking a toxic waste pool, followed by the infamous "swastika room" (changed in Doom 1.4) where computer mainframes sink into the floor. This is followed by a room containing the exit portal...but you can't exit yet, since there's a chasm in the way and a switch needing to be found.

Instead, turn left (or backtrack). Go past the stage area, and pass through the [blue door] blue door to a steel-panelled maze. You're free to explore the maze if you wish...but if you want to cut to the chase, turn due right, follow the long, straight passage till you hit a wall, then turn right again and follow the left wall to a window with the [yellow key] yellow key. Next, follow the staircase to a latticed platform. Hit the switch on the wall, then venture out through the [yellow door] yellow door to see a platform in the exit room rise. You may wish to venture into the swastika room if you haven't been there already. Otherwise, go up the stairs, and take the exit.

The yellow key is not technically necessary to complete the level, although it is required to pass through the room it's in.

Gallery

April 1993 alpha map, with numerous differences from the final version. Lockers and showers are present in the east corners, no exit portal is present, and the level is contained within a six-sided floorplan.

Detail from May 1993 intermission screen, designating this level as a "recreation & training centre."

May 1993 alpha map with no showers, no lockers, a widened maze, a smaller central room, and the addition of a toxic river and exit portal. By this point, the level was much closer to its final form.

December 1993 map from the initial shareware release, featuring the infamous "swastika room" that was inserted to reference Wolfenstein 3D. John Romero reconsidered this after receiving an impassioned letter from a veteran of the Second World War, and the symbol was changed in version 1.4.

E1M4's stage area, a holdover from the alphas and the level's original purpose as a recreation centre.

"Command Control," as depicted on the intermission screen in the final game.

E1M5: Phobos Lab

"Phobos Lab" contains the most secrets, by far, of any level in the first episode of the game. Enjoy the scavenger hunt!

You begin in a low-ceiling room bisected by a river of toxic waste. Wade across, follow the corridor to the left, and step out onto a balcony overlooking a toxic pool. A narrow platform on the opposite wall will rise. Backtrack down the corridor, take a right up the stairs, and scrutinize your surroundings. 1 ▶ There's a discoloured panel to the right, hiding a room with a shotgun. Walk out onto the narrow platform that rose earlier. Follow the passage to the end, and you'll find the [yellow key] yellow key flanked by candelabras.

Backtrack to the room with the narrow platform, and jump into the toxic pool below. 2 ▶ Look for a discoloured panel on the wall ahead: It's a hidden door to a rocket launcher and other goodies. Follow the passage that leads beyond, and you'll be back in the corridor near where you started.

Take the door to the left of the stairs. It opens outdoors to a toxic waste pool with a perimeter walkway. Follow this walkway to its midpoint, then go through the [yellow door] yellow door. A lift drops down to a grand staircase, which leads you to a semicircular observation area flanked by two pillars in yet another toxic pool. A vast array of secrets awaits. 3 ▶ Open a hidden panel in the outer alcove to get a radiation shielding suit. 4 ▶ Open the left wall of the last area to reveal a chainsaw. 5 ▶ Behind the chainsaw is yet another hidden door, leading outside to a soul sphere. Go back indoors, and wade across the pool to hit the switch and drop the pillars. ▶ ▶ Ride each pillar to reach a corresponding ledge containing armour or ammo.

As you return up the stairs, you'll notice that two trap areas have opened, and the upper alcoves in the corners now have connecting lifts. 6 ▶ Take the left lift to the top, and feel the wall: A hidden door will open (Doom 1.2 and later only), followed by ▶ a second door. Inside, you'll find a Hell-corrupted room with an invisibility sphere and a red pentagram on the floor. The pentagram is the first accessible teleport you'll encounter in the game: If you touch it, you'll be transported back to the beginning of the level. ▶ Otherwise, take the southeast passage to a semi-hidden door opening to the perimeter walkway.

Across from the yellow door and central waste pool is a short passage ending in a room facing the candelabras. ▶ A hairpin turn to the right will reveal a hidden medikit. Collect this if you need it, then follow the blue steps to the computer room. 7 ▶ There's a hidden door on the right wall, just left of the overhead "bridge:" It reveals a room with a chaingun and computer area map. Next, hit the switch in the corner: Another wall panel will open, revealing a dark passageway. This leads to the [blue key] blue key, and yet another switch. Take a hairpin turn to the right and you'll see a narrow staircase down, bringing you to the [blue door] blue door. What lies beyond is a space that was positively frightening by the standards of 1993: A pitch-black cave punctuated by a strobing light, vertical pillars, enemies, and exploding barrels. ▶ Go straight ahead into the alcove that faces you: The entire back wall opens as a door. 8 ▶ A hidden alcove just left of where you entered contains a light amplification visor. 9 ▶ A slime-coloured patch on the west wall is a hidden blue door leading back to the pentagram room. Finally, an alcove in the north wall leads to the exit.

Gallery

December 1993 map from the initial shareware release, lacking the Hell-corrupted pentagram room added in Doom 1.2.

The computer area map and light amplification visor both make their first appearance in this level.

The pentagram room with teleport, added in Doom 1.2.

"Phobos Lab" is depicted on the intermission screen as having a central hub and four wings. It also straddles a ridge separating the first four levels from the last three, echoing the division between "everyday" and "restricted" areas suggested in Tom Hall's Doom Bible.

E1M6: Central Processing

"Central Processing" was created by John Romero, and experienced some of the most dramatic development of the game. In early alphas from April and May 1993, the strategic elements of the map were spread around an octagon-shaped waste treatment area that was visually impressive, but served as deadweight in gameplay. Most of this area was eliminated from the layout of the final map. Even cut down to its final incarnation, this level remains one of the largest physical spaces in Doom.

You begin at the south edge of the former octagon. The perimeter walkway has been stubbed off, but two treatment pools remain. Take a right on the bridge that crosses them, and enter the large room with vertical partitions. The [Red key] red key is at the far end...but be alert. ▶ Five hidden doors around the room will rise, ambushing you with additional enemies...and items.

Go back over the bridge, following it in the opposite direction. ▶ When you reach the second bend, look right: There's an opening in the wall that leads to a room with bonus items. Proceed through the pair of [Red door] red doors. These lead to a platform overlooking a darkened pool filled with toxic waste. The [blue key] blue key is at the edge. ▶ As you approach, a door will open behind you revealing a demon and health items. Now take the key, and jump into the pool below. ▶ Bear right for a radiation shielding suit. 1 ▶ Bear straight ahead for a passageway leading to a soul sphere. 2 ▶ And bear left to reach a platform with bonus items, a hidden staircase with bonuses more, and a one-way door returning you back to the starting area.

Straight ahead, beyond the treatment pools, is a door. It opens into a central control area with passageways radiating in five directions, three of them blocked by yellow doors. Take the right (east) passage. After you cross the waste treatment pool, you'll hear a platform move. ▶ Turn around, and a hidden room will have opened revealing a radiation shielding suit. Don't take it yet, though: You'll need it later.

Continue down the passage, and go through the [blue door] blue door. This brings you to a maze of waste treatment tanks connected by walkways. Go straight through the first tank, turn left at the second, ▶ then look for a discoloured panel on the left wall of the passage beyond: This hides a computer area map. Bear left at the next fork, and continue until you see a switch. Flip it. Go straight ahead at every fork through the next two tanks. It ends at an observation platform, where you'll find the [yellow key] yellow key.

An ambush will open behind you, unleashing one to three spectres. 3 ▶ Feel the wall to the left of the window: A hidden blue door will open, leading to a rocket launcher, invisibility sphere, and backpack. ▶ On the landing below, feel the right wall. It's another hidden door, bringing you back to the room with the radiation shielding suit that you saw earlier. Pick up the suit, then dash over to the winding passageway on the opposite side of the pool. 4 ▶ A barrier has opened up, allowing access to a platform with health, ammunition, and armour. Open the door: It drops down to an outdoor area with a soul sphere atop a movable column. ▶ Ride the column up, then use a hidden door to go inside.

You're now in the north end of the level, past the central control area. Since you've bypassed a portion of the level, you may wish to take a left and explore the areas between your entry point and the [yellow door] yellow doors. ▶ A radiation shielding suit and health items are available in the toxic pool. When you're done, take the stairs onto the raised platform at the far end, and flip the switch between the candelabras. A door will open in the room to the south, revealing a side area with three sets of stairs. Take the stairs up if you want a medikit; otherwise, go down. Hit the switch on the wall to reveal the exit.

The yellow key is not strictly necessary to complete the level, although it is required for backtracking. Some of the doors on this map are time-delayed...so if you're stuck where you are, wait.

Gallery

April 1993 alpha map, showing the octagon-shaped waste treatment area that the level was originally built around.

May 1993 alpha map, with a secret passage added and a maze area deleted.

"Central Processing," as depicted on the intermission screen.

E1M7: Computer Station

"Computer Station" is the penultimate level of Episode 1. As with "Phobos Lab," it's a John Romero creation characterized by railed balconies over toxic pools.

You start in an interstitial room. Proceed through the doorway to a lobby with a raised platform, and passages branching out in multiple directions. You'll notice a soul sphere through the window on the right side, but you can't get to it yet. On the left side, there's a computer room housed in a recess in the wall. Take the lift in the corner, walk to the end of the gallery, and pick up the [yellow key] yellow key.

Head out of the computer room, bear right, and you'll arrive at the [yellow door] yellow door. Inside is a room with a cluster of mainframes in the centre. ▶ Take the lift under the flashing light to collect bonus items and a rocket launcher from atop the machines. Then, follow the well-lit corridor south to a bridge with a cylindrical column in the middle. The column will lower as you approach, enabling you to jump off in either direction. What you choose to do next depends on what your priority is:

Exploring the passages beyond the column (do this first if you want to eliminate backtracking):
Just beyond the column, the passageway forks in two. The right fork meanders a bit before leading to a balcony, a large room, and a lift to a dark observation area where you'll find the [red key] red key. The left fork had more significance in alpha development, where it led to the northwest corner of the map...but in the finished game, it stubs itself off in an elevated computer room. A chainsaw is housed in an enclosure here...although it won't be accessible until you activate a switch elsewhere in the level.

Gathering secrets around the column (do this first if you need the chainsaw):
1 ▶ Jump into the south pool, and follow the platform and passageway that opens to retrieve a chaingun and backpack. ▶ The next step is a bit tricky. Hop back onto the column, face north, and RUN in the direction of the balcony you see on the right wall in the distance: There's a computer area map waiting for you here! ▶ Now drop into the pool, and head to the opposite corner. There's a radiation shielding suit, and a switch on the wall. 2 ▶ Hit the switch: A passage will open, leading you to a hidden area with bonuses and a second wall switch that controls the aforementioned chainsaw enclosure. ▶ Return to the toxic waste pool, and turn right: The column to the right has a megaarmour hiding in it. 3 ▶ Follow the pool north, and you'll be able to collect the soul sphere you saw earlier. A one-way door will open, returning you to the starting area.

Once you're done, go through the [red door] red door in the starting area and collect the [blue key] blue key from the balcony. ▶ An ambush room in the lobby will open, netting you a few bonuses. Walk to the well-lit corridor entrance in the central computer room: Between the light panels and to the right, an alcove will have opened. 4 ▶ The left wall of the alcove is a hidden door leading to an outdoor area with an invisibility sphere.

Travel to the [blue door] blue door (just south of the last secret on the map), and follow the stairs up to a rectangular room with multiple ways out. The right passage leads to a switch that opens the door to the left passage, which leads you to the exit. Originally this room also had a third passage emanating from the centre, but this was eliminated in post-alpha development.

Gallery

April 1993 alpha map. It differs vastly from the final version, with additional passageways extending around the west and south sides of the level, and no outdoor areas.

Detail from May 1993 intermission screen designating this level as a "refinery," evidenced by the toxic vats that appear throughout.

May 1993 alpha map, differing chiefly in the reshaping of the exit passage. The passageways would be reshaped further in post-alpha development.

An observation window overlooking the platform with blue key.

"Computer Station," as depicted on the intermission screen in the final game.

E1M8: Phobos Anomaly

After clawing your way through the UAC techbases of Phobos, you've finally arrived at the Anomaly: An interdimensional portal to Deimos, guarded by Barons that will do anything to keep you out! This level was created by Tom Hall, and originally featured a cavern looping around the entire corridor. Subsequent in development, it was modified by Sandy Petersen to feature a dramatic pentagram-shaped stage and levitated ceiling, foreshadowing the cosmic horror of episodes 2 and 3.

Hit the switch on the wall. The barrier lowers, revealing a room below with a toxic pool and circle of exploding barrels. ▶ Hop aboard the lift on the opposite side of the room to get a computer area map. ⚠ Once the lift rises, it cannot be brought down again without stepping onto the platform at top.

North of the pool, a staircase leads down. 1 ▶ Near the base of the stairs, there's a slime-covered wall panel hiding a soul sphere. Go through the door into a cross-shaped room: Stubbed-off remnants of the cavern from the alpha versions branch off to the left and right, with a shotgun and chaingun within.

Now it's time to face the bosses. Follow the long corridor past the ominous torches, and hit the switch at the end. A lift will rise, placing you in the epicentre of the pentagram. Two doors will open, revealing the twin Barons of Hell: Hideous, bug-eyed monsters that lob green projectiles at you. Run circles around the Barons, lobbing rockets if you have them. Each Baron "closet" has an ammunition box in it. ▶ The right wall of the right closet contains a hidden panel over a switch that lowers the lift (Doom 1.666 and up only), enabling you to return to the beginning rooms of the level. In addition, an invisibility sphere is present in one of the points of the star.

Once the Barons fall, the outer walls of the pentagram will lower. Drop down to the surrounding courtyard, and go to the only place available to go: The concrete enclosure on the north end. A switch will activate a staircase to the top. Step onto the teleport with the Baron's face...and get ready for the fright of your life. You'll be transported through another dimension to an inescapable ambush, mauled, and left for dead.

Like it or not, this is the only way to the lost Deimos base...and to Hell.