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Chaos (zs_chaos) is the fifth chapter of Zombie Scenario: Season 1 in Counter-Strike Online.


This map has no fixed number of rounds. The route chosen by majority will affect the outcome. This maze has the minimum of 4 rounds and maximum 7 rounds.

In boss round, the player has to fight against Siege Type Phobos. Voodoo Zombies will appear at a certain time during the boss fight. If they come close to Phobos, the later one's health will be recovered.

Deimos makes it first appearance in zombie scenario in this map with its signature ability to drop the weapon wielded by the targeted human. It has greater hit points than normal zombies.

Official Description[]

A troop transporting the samples have left. The others entered the laboratory complex according to the last clue. All of the buildings in the laboratory complex are connected to each other towards the basement passage, and the size is much bigger as compared to with what they seen outside. An urgent retreat order from government has been delivered to troop Captain Choi Ji Yoon in border while we was about to start our investigation by entering the basement passage.

However, Captain Choi behavior changed suddenly when we reported to her about the current location of our troop. She ended the communication with the headquarters and requested us to conduct an internal investigation in the laboratory complex. If we continued on the investigation, it seems like we are ignoring the retreat order from the government, however, our will that led us to this place has already accepted her request.

What was she really trying to find out..?

- From rescue team signal corpsman 'Felix's diary'.


  1. The rescue unit is divided into a transport unit to transport the samples obtained and a search unit to continue the investigation, and the search unit follows the Last clue and infiltrates the research complex.
  2. At the request of Choi Ji Yoon, a member of the intelligence agency, she begins to explore the research complex and gradually approaches the core facilities.
  3. In order to eliminate the intruder, three Siege Types were simultaneously released for combat, but since they are still unfinished, Siege Type Oberon and Dione attempt to escape from the lab.
  4. The search force, which suffered heavy damage from encounters with Siege-type Oberon and Dione, tries to track the two fleeing dogs, but a Siege-type Phobos appears in front of them.
  5. The search force succeeded in defeating it after a fierce battle with the Siege-type Phobos.
  6. CF. Choi Ji Yoon is a member of the Intelligence Agency and is investigating some kind of relationship between counter-terrorism, terrorists, and the government and the shadow government. While she is being marked for pursue by Ritsuka, a member of the Red Army faction in Asia, she gets information that Dr. Rex is currently being helped by an unknown military company and infiltrates the research complex.
  7. CF. May follows behind her to observe an intelligence service agent acting alone.
  8. CF. The Siege Type Phobos was produced as a combat type, unlike the prototype for testing. It's a much more intimidating target than before, but if you defeat it, you'll get a lot of samples to help with your anti-zombie research.


  1. This is Ji Yoon Choi. Search team, can you hear me?
  2. I’m so relief that you are still alive.
  3. I got a withdraw order from the government, so I came here to help you guys.
  4. You are at laboratory basement now? Why did you enter that place?
  5. Um.. OK, fine. I will help you to escape from there.
  6. But, before that... I got one request for you.
  7. Please investigate thoroughly, especially the inside of the laboratory complex.
  8. I believe that you can do it. Good luck to you.
  9. I guess the defense system has been operated!
  10. I’m trying to cancel the system. Please earn more time for me!
  11. You can use the block system, so please control it with E key button!
  12. It looks like they are coming in a huge group!
  13. Please endure for a little longer!
  14. I have cancelled the system successfully. Get to the exit now!
  15. We need to choose either red or blue arrow.
  16. I will support the side where the majority choose.
  17. There are lots of reaction of a living body nearby. You better be careful.
  18. I will try to find the exit way, so please follow the road to proceed.
  19. It seems like they have found you guys!
  20. A huge group is approaching there now!
  21. I will let you open the door with E key button. Come out from there quickly.
  22. You have reached at the exit! Open the door with E key button and escape from here!
  23. We need to choose either red or blue arrow.
  24. I will support the side where the majority choose.
  25. What kind of reaction is this from a living body that is so huge?
  26. [Operate Siege type attack system]
  27. [Allow to use 3rd Siege type]
  28. [Oberon, Phobos, Dionne have been released completely]
  29. Siege type...? Phobos?
  30. This is the name of the prototype which you have seen before?
  31. Wait a minute. I have found a document stating their destination is the government laboratory!
  32. They might destroy the laboratory..! We need to report this immediately.
  33. All of you need to escape to a safe place quickly!
  34. I received an order from the government to kill them immediately.
  35. Firstly, you guys need to cooperate with us to...
  36. Be careful! One of them is approaching to here!!
  37. That is... Siege Type Phobos...??
  38. We need to tie his leg. Stop him now!
  39. The remaining zombies are going to that place!
  40. Alpha squad, please respond!
  41. Siege type Oberon is going out from the laboratory! Alpha squad!
  42. Delta squad!
  43. Siege type Dionne is going out from the laboratory!
  44. Oh my god.. How can we receive such damage from only two...
  45. We need to have a change of plan. We will pursuit the two that came out.
  46. Please survive, I hope to meet you again alive...
  47. -Communication with Ji Yoon Choi has been disconnected-
  48. [Phobos has released his healing troop]

Release date[]

Chaos was released on:

  • South Korea: 14 July 2010.
  • Indonesia: 13 June 2012.
  • CSN:Z: 23 September 2014.


  • Recommended to use weapons with at least "A" grade in scenario.
  • There are some parts of this map that are not accessible by zombies.
  • Always share if you have powerful weapons.

It is very much like fighting the boss from Last Clue, however voodoo will appear at a certain time to heal Phobos. Kill it immediately before they recover Phobos' health.


The number of rounds it takes to reach Siege Type Phobos can range from 4 to 7 rounds. Players will prefer to clear the map in only 4 rounds if possible to cut time.

There are 4 types of rooms:

  • A1, Sewers - Starts at the double doors that need to open at the switch. This is Pursuit Round with at least three doors that need to be opened with switches and one barrier. A2 is where players start behind the barrier instead.
  • B1, Console Room - The room with the door console at the left side, survival room. B2 is the same room with the door console at the center of the room.
  • C1, Warehouse - The warehouse room without the forklift blocking the stone fence, close to the blue doors and red door on the opposite side. C2 is the same room, but with the forklift blocking a part of the fence close to the blue doors.
  • D, Boss arena.

Guidelines to reach Siege Type Phobos battle arena within 4 rounds:

Chaos pursuit route
If you have the first round with Pursuit room, the route you are taking is BLUE - RED - RED

Chaos survival route
If you have the first round with Warehouse room, the route you are taking is RED - BLUE - RED

If you have the first round with the door controls in the middle of the room, the route you are taking is RED - BLUE - BLUE

Chaos 2door route
If you have the first round with the door controls on the left, the route you are taking is RED - BLUE - RED


Honor mission
Title Description Task
A medal given to players who have killed Phobos for 100 times
[Phobos Slayer]
Gentleman, rumor has it that the monster has a blue color skin and some terrible things on its hands. I really want to meet the person who defeats such a monster for more than 100 times. Note: Easy stage is not included. Defeat Phobos 100 times.



  • This is the only map with unfixed number of rounds in Zombie Scenario.
  • In Indonesia region, this map was released after Dead End.
  • There is no specific starting point in this map.
  • This is the first Zombie Scenario map that introduces Deimos.
  • After 26 March 2015 update in South Korea, several adjustments have been made in Chaos:
    • The door opening speed has been greatly increased.
    • Some zombie pathways have been removed, leaving blank walls.