MAP20: Interstellar Sickness (Community Chest 4)


Community Chest 4 maps 12-20

01 02 03 04 05 06 07 08 09 10 11
(12 - 20)
21 22 23 24 25 26 27 28 29 30
Secret maps: 31 32
Bonus map: 35

This level occupies the map slot MAP20. For other maps which occupy this slot, see Category:MAP20.

MAP20: Interstellar Sickness is the twentieth map of Community Chest 4. It was designed by Chris Kassap (lupinx-Kassman) and uses a MIDI of "We're the Robots" from Mega Man 9 sequenced by Jace.

Interstellar Sickness was featured in Doomworld's Top 100 Most Memorable Maps, placing 18th.


Map of Interstellar Sickness
Letters in italics refer to marked spots on the map. Sector, thing, and linedef numbers in boldface are secrets which count toward the end-of-level tally.


The first of Kassap's two contributions to Community Chest 4 has a relatively simple start, but picks up the difficulty level about halfway through, ending in a spectacular sequence where you cause two spiderdemons to infight and run rings around a cyberdemon with the use of teleporters. While you admire the amazing architecture and detailing, don't forget about the angry hordes seeking to end you.

Part One: Yellow Key

You begin the level with a shotgun. Flip the switch in front of you to raise the floor. Head forward, grab the backpack from its pedestal (and read some backstory via the computer panel next to it). Follow the corridor to its end and step into the teleporter.

You will be teleported to one end of another long corridor. Hear, you will face the first opposition of the map: five zombiemen, four imps and a chaingunner in the back (Ultra-Violence and above only). Peek with the shotgun to mow them down. If you are on Ultra-Violence and above, see if you can get the chaingunner to do some of the dirty work for you. Head forward and grab the box of ammo at the corner. At the corner watch, for another four imps and continue forward into an area with a platform and a switch. As you enter, watch to the left for a shotgun guy waiting in ambush. Grab the armor near where it was, then kill the three imps in here. Flip the switch next to the platform, revealing it to be a lowering door. Kill the chaingunner ahead and flip the switch to lower the second of a pair of platform-doors.

This will take you to the first large area of the map, a vaguely square platform with four walkways leading into a central area. Kill the two shotgun guys behind the door first. This area is filled with zombiemen and imps, but there's a good number of health bonuses and armor bonuses on the walkways. Use your chaingun to mow down the cannon fodder and fill your health and armor up. Once ready, head to either door in the northwest, clear the two shotgun guys inside and flip the switch. As you do so, you might want to take the chance to clear out some imps visible through the window near the switch (and if possible, a pair of demons and a pair of chaingunners in the distance).

Go back out to the large area, and head through the door in the west. This takes you to the area beyond the window near the previous switch, Clear out any stragglers. At the junction, head down the steps and go south. This takes you to an L-shaped area with six zombiemen on a raised ledge, five imps ahead and a mancubus (not on Hey, not too rough and below). From isolated platforms to the south and east, two groups of a cacodemon and two imps will attack. You will also have to deal with more imps and a Hell knight on a pillar in the region directly in front of the switch at the end. See if you can get the mancubus to do the heavy lifting for you in this crossfire.

Flip the switch at the end of the L-shaped ledge, then go back to the junction. This time, head east (and grab the berserk pack in the alcove). Continue south to the area with the Hell knight on a pillar. As you approach, watch for a window to the left (southeast) with a chaingunner. Continue south and open a door ahead to a room with the super shotgun on a pedestal. Pull out your chaingun and clear out the first group of two chaingunners and four imps, head in and clear out the three zombiemen and shotgun guy approaching from the sides. All this while, watch for fire from the mancubi in the outside area.

Proceed left (east) from the super shotgun and open the door. Kill the three zombiemen ahead, then kill the shotgun guy on either side of the T-junction. First, go north and flip the switch at the end. This lowers bars in the south, but also opens a trap in the corner with two zombiemen and a Hell knight (a shotgun guy on Hey, not too rough and below). Use your super shotgun to hold them at bay. Next, head back to the T-junction and head south. Head out into the outdoor area, but watch for two imps in pillboxes to either side of the exit.

As you exit into the outdoor area, five imps suddenly appear from the floor. You will also have two more imps in the northwest to handle. Quickly take them out with the chaingun and go for the rocket launcher in the middle of the area, which you can sue to take out the mancubi. Go all the way south, then west towards a door. Just before the door, watch for a shotgun guy in a small alcove to the left.

Open the door and kill the two zombiemen and shotgun guy in front, but watch for the pair of zombiemen to the left. head up the curved staircase and clear it of imps. At the same time, you will have to watch for three cacodemons that will harass you from the left (west). As you reach the top, two more floor traps will spring, releasing four more zombiemen ahead of you. Kill them, then deal with the Hell knight on the grey block. Next, flip the switch in the east to open another platform door. Again, kill the two zombiemen and shotgun guy in here. Punch out the three demons and chaingunner on the curved staircase, then make your way to the top. Flip the switch next to the Hell knight's block to lower the bars in the west.

Head west. This next area is trap-infested. As you head up the curved staircase, the following traps are released in sequence:

  • Three floor traps nearby activate, releasing three imps nearby.
  • The two chaingunners in the southern structure are awakened.
  • The forcefield in the two structures in the east and west deactivate, releasing two cacodemons.

Head south, walk around the structure and pick up the yellow keycard. As you pick it up, bars close at both sides around the structure, while the middle set of bars lowers and three revenants teleport in. This is a nasty one. Try to put a rocket into the first one before it enters super shotgun range. Bait the revenants into punching instead of firing missiles, and you can deal with them easily.

Go northwest of the curved staircase you used to enter this area and flip the switch to open the yellow bars. Step into the Plutonia-style teleporter to be teleported south of the first large area of the map.

Part Two: Teleporter Frenzy

Head north and press the switch left of the door to open a shortcut back to the first large area. Head to the north and open the door flanked by yellow bars. Kill the Hell knight inside and flip the switch. This lowers the yellow bars in the east. Head there and step into the Plutonia-style teleporter.

You are now in the middle of a circular area at the north of the map. Press on any of the surrounding pillars to lower them all. Once you step off your initial position, monsters are going to start pouring out of the three teleporters in the west, south and east. In total, five imps and three chaingunners (eight imps on Hey, not too rough and below) will come out of each teleporter. Quickly head north, grab the plasma gun and bulk cells, then flip the switch (the pillars will take some time to lower). Use plasma to suppress the enemies coming out from each teleporter.

Once the pillars have lowered, head out to the outer walkway. As you head outside, another set of floor traps will activate, releasing two shotgun guys and six zombiemen. From here, you can go in either direction (although you should go right to clear out some imps at the ledges you will teleport to later). As you continue along the outer walkway of this area, 12 floor traps will activate, releasing 12 Hell knights into the area. Rockets are suggested for use on them. As you head to the east side of this area, look east and put some rockets towards the two isolated ledges with imps on them - you are teleporting there later. At the south, you also need to be careful of imp fireballs from the south.

From the south side, head into the central area again. You don't have to worry about any of the revenants in the pillars for now. At either side, kill the Hell knight in the cage, deal with the demons in the lowered area, then follow the dry land around to an area with a metal panel with a red circle. This teleports you to one of the ledges in the east. Flip the switch at the end, then teleport back. You need to do this on both sides of this area to lower the two sets of bars in the south. Once done, head south, save your game (you'll need it), then step onto the teleporter pad with the red circle.

Part Three: The Finale...?

This next part is significantly more difficult than the previous parts of the level, so be prepared.

As soon as you teleport in, you find yourself in the middle of a four revenant crossfire. Quickly grab the megaarmor ahead, but doing so causes two arachnotrons to appear nearby. Your best bet is to quickly take out the arachnotrons, then use the cover on their level to take out the revenants. In a worst case scenario, just use the teleporter pads to jump back and forth between this area and the previous area.

Ride the platform up and head east along the bridge, clearing out any imps you see along the way. As you cross the halfway mark, a baron of Hell will appear on each of the green and red pillars flanking the bridge. Continuing east, watch for four chaingunners hiding among the computer panels. Head up the steps, grab the nearby megasphere and bulk cells, and prepare for a bad time.

As you headed up the steps, two alcoves next to the exit door opened, each with a spiderdemon. Each alcove contains a keyed switch - you must flip both to open the exit door. At the same time, a huge horde of monsters is going to pour out into the area. In total:

  • Hey, not too rough and below: 48 zombiemen.
  • Hurt me plenty: 24 zombiemen, 12 shotgun guys, 12 revenants
  • Ultra-Violence and above: 24 zombiemen, six shotgun guys, 18 revenants

Get the spiderdemons to mop up for you, and when they're done you can even get them to mop each other up through monster infighting. While they are busy, you might as well get the red and blue keys. North and south of this area, there are areas with cages of light that are actually teleporters:

  • The north one takes you to a one-on-one duel with a cyberdemon in an area with invisible floor. The architecture works to the cyberdemon's disadvantage, as you have the benefit of some teleporters. Burst it down and take the red key it was guarding to be teleported back.
  • The south one takes you to a garden-like area. Kill the four imps here. Flip the switch in the lake and three arch-viles will teleport in. Kite them around the green rocks in the northwest or the southeast. The south side of each rock will have a newly revealed switch panel - flip both to lower the blue key in the north. take the teleporter back.

Flip the switches in each of the spiderdemons' alcoves to open the exit door. In this last darkened corridor, you just need to watch out for the Hell knights and the crushers. Attempt to open the door at the end to end the level, but that's only the halfway mark of what Kassap has in store...

Other points of interest[edit]


  1. In the first big area you come across, head for either northwestern door. Look out of the west window for a switch to shoot. Shooting it reveals a chainsaw to your right. (sector 986)
  2. In Secret #1, open the left wall for a megaarmor and a Megaman-like rendition of Doomguy. (sector 933)
  3. Flip the other switch near Secret #1, then head back to the big area and take the door that the bars had previously blocked. Head straight south from there until you reach a hall with red computer panels and zombiemen on a ledge near them. Use the lift to go on this ledge, then go to the other end, pushing the red button. This opens a computer panel north of you with a partial invisibility. (sector 1313)
  4. Enter the room with the super shotgun and take a left at the fork. Open the door and take a right at the next fork. There will be a section of damaged wall here, so lower it for a teleporter. Enter it to get a soul sphere and the words "Who's IN SPACE?" as well as a picture. (sector 1541) Note that if you go on the walkways where imps rise up and head for the southwest door, there will be an additional hint for the teleporter in the form of a dark arrow.
  5. At the final area, one of the terminals left of the exit door has "TEI TENGA" on it. Lower it for an invulnerability. (sector 26)


  • Three orange pads in the west side of the map have tags 16, 17 and 27 and teleport landing things within them, but no line is tagged to teleport to any of those sectors.
  • In the southwest of the map, there is a set of lines with tag 57 and action "W1 Floor Lower to Lowest Floor", but there is no sector with tag 57.

Demo files[edit]

Areas / screenshots[edit]


Current records[edit]

The records for the map at the Doom Speed Demo Archive are:

Run Time Player Date File Notes
UV speed
NM speed
UV max 9:04.80 Dylan Gill (TheV1perK1ller) 2017-05-23
NM 100S
UV -fast
UV -respawn
UV Tyson
UV pacifist

The data was last verified in its entirety on April 3, 2022.


Map of MAP20's deathmatch arena

This level contains its own, separate deathmatch arena based on Kassap's Late Outpost from 32in24-6. It has been fully retextured, mostly using the resource pack created for Community Chest 4, with additional detailing on one side of the building. The teleporters in the damaging fluid (changed from lava to nukage) have also been rearranged, and the teleporter northeast of the BFG9000 teleporter was removed. Finally, the pillar that must be lowered to access the teleporter is now one sector rather than two. It is otherwise identical to the original map.

Under construction icon-yellow.svgThis article or section is a stub. Please help the Doom Wiki by adding to it.

Player spawns[edit]

This arena contains ten spawn points:

  1. facing north-east. (thing 727)
  2. facing south-west. (thing 728)
  3. facing north. (thing 746)
  4. facing north-east. (thing 757)
  5. facing north. (thing 764)
  6. facing south-east. (thing 827)
  7. facing north-east. (thing 830)
  8. facing north-east. (thing 835)
  9. facing south-west. (thing 838)
  10. facing west. (thing 843)


The following things (per skill level) are placed in the arena:

Weapons 1-2 3 4-5
Chainsaw 1
Shotgun 10
Super shotgun 1
Chaingun 5
Rocket launcher 1
Plasma gun 2
BFG9000 1
Ammunition 1-2 3 4-5
Box of bullets 5
4 shotgun shells 22
Rocket 12
Box of rockets 5
Energy cell 11
Energy cell pack 1
Health & Armor 1-2 3 4-5
Stimpack 10
Items 1-2 3 4-5
Armor bonus 33
Health bonus 8
Backpack 10
Miscellaneous 1-2 3 4-5
Deathmatch start 10
Teleport landing 7


Map data[edit]

Things 933
Vertices 20923*
Linedefs 18749
Sidedefs 33286
Sectors 1735
* The vertex count without the effect of node building is 15830.


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

Technical information[edit]

Inspiration and development[edit]


  • After the map got onto the Top 100 Most Memorable Maps list, Chris Kassap wrote a forum post which reveals the backstory behind MAP20-MAP21, as well as a few development trivia.

See also[edit]


External links[edit]