MAP21: Mt. Erebus (Console Doom)

MAP21: Mt. Erebus is the twenty-first level of console versions of Doom, based on the original E3M6: Mt. Erebus with modifications made to adapt to the consoles' limitations. It was converted by American McGee and originally designed by Sandy Petersen. The map first appeared on the Atari Jaguar, and was later ported to the 3DO, Game Boy Advance, Sony PlayStation, and Sega Saturn consoles.

Essentials
Turn right and head over the lava pool to the next platform. Once across, turn left to see a marble brick building in front of you. Head towards this building - on I am a Wimp and Not Too Rough skill levels, the blue skull key is located in front of the door to this building, allowing you to go straight to the level exit. On Hurt Me Plenty and Ultra Violence, you will need to explore more of the level to find the blue key.

Hurt Me Plenty and Ultra Violence

Go through the door into the marble brick building and kill all the enemies inside. Look at the south-west wall and you will see a candle between two small staircases; open the wall behind the candle to reveal a teleporter and step through it. You will find yourself outside a square brick building - go round to its east side and press the gargoyle switch in the alcove which will let you inside. Press the switch directly ahead of you to open a metal wall behind you, revealing the yellow skull key.

Take the key and go back outside. Go to the north side of the building and open the yellow door, then go through the teleporter behind it. You will be inside a Y-shaped building - turn around and follow the path to a fork, and two doors will open in front of you revealing enemies. Go down the left-hand fork and kill the enemies guarding the blue skull key, then go down the right-hand fork and kill the enemies blocking your way to a switch. Press the switch and return to where you started; a wall has lowered allowing you to get out of the Y building.

Exit

If you found the blue key in front of the marble brick building, head due west until you see a brick building in lava next to a metal structure. If you found the blue key in the Y building, then head south and west around this building once you get outside it. Drop into the lava and head towards the brick building; as you approach, you will see some nukage on the floor leading inside the metal structure. Follow the nukage to a blue door, go through it and continue on to the exit door. Go through this and step on the teleporter pad to finish the level.

Other points of interest

 * The building in front of you at the start of the level has a box of shells and a medikit on its top floor, along with several enemies.
 * North-west of the aforementioned building is a round marble structure containing armor, a box of shells and a stimpack. When you approach these items, the brick structures on either side will open to release enemies. The north-east structure contains a box of bullets and an invulnerability powerup, useful for this level's many damaging floors.
 * The west side of the main island has a metal staircase - climb up it and drop off the top to reach a small island with several enemies. There is a second invulnerability powerup directly below the top of the staircase you can use to escape this trap. The red platform on this island holds a shotgun, a chaingun, a rocket launcher and a box of rockets.
 * On the south-west of the main island is a narrow walkway leading to a small island, with pickups including two boxes of shells, two boxes of bullets, a box of rockets and several armor bonuses. When you step off the end of the walkway it will fall into the lava; you will have to cross the lava to get back.
 * The brick building by the passage leading to the exit contains a soulsphere and several cacodemons. It opens when you leave the Y-shaped building, which is certain to happen on Hurt Me Plenty and Ultra Violence but is optional on lower skill levels.

Secrets

 * 1) Go inside the brown brick building in the north-east of the level. Inside are two teleporters. Take the one in the south-east corner, and you will be taken to a ledge with a plasma gun on it. (sector 67)
 * 2) Inside the marble brick building, open the north-eastern section of wall between the two staircases indicated by a candle. It will reveal an alcove containing an energy cell pack. (sector 104)

PlayStation only

 * One of the walls inside the marble brick building, next to the wooden door, is distorted due to a wrong Y-offset setting (linedef 341).
 * On Ultra Violence skill level, a demon and a spectre inside the brick building in the separate east part of the map (things 73 and 74) are stuck due to overlapping bounding boxes.

Comparison of versions
Numerous changes exist in the level as compared to its PC version:

Removed areas

 * The water pit and all the buildings inside it are removed.
 * Most of the lava surrounding the islands is removed, along with all but one of the small buildings in the lava. Only the building near the passage to the blue door, which contains cacodemons, remains.

New design

 * The square building on the east side of the level is completely cut off from the rest of the level. It can be accessed using the hidden teleporter in the marble building on the north side of the map (on PC, this teleporter sends you to a building in the now-removed water pit). After teleporting to the building, you must enter it and find a yellow skull key, which opens a nearby door revealing a teleporter that sends you to the Y-shaped building holding the blue skull key on higher skill levels.
 * The window at the top of the building in front of the start point has been removed.
 * The four alcoves in front of the marble building, which contain imps, are larger and have walls in front of them instead of grate textures.
 * The blood in the passage leading to the blue door is changed to nukage.

Other

 * This level has no secret exit due to the removal of the water pit, and the absence of the Warrens level. The next level with a secret exit is MAP29: Twilight Descends, which takes you to MAP57: The Marshes.

PlayStation
Some additional changes were made in the PlayStation port:
 * A mancubus is added to the island on the west side of the level on Ultra Violence.
 * The blue door uses a wooden door texture instead of a skull bar texture.

Music
The map uses the following music tracks:

Player spawns
This level contains six spawn points:
 * 1) facing north-west. (thing 215)
 * 2) facing north-east. (thing 216)
 * 3) facing south. (thing 217)
 * 4) facing south. (thing 218)
 * 5) facing south-west. (thing 219)
 * 6) facing south-east. (thing 226)

Things
This level contains the following numbers of things per skill level: