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Last Clue
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Last Clue (zs_lastclue) is the fourth Zombie Scenario map in Counter-Strike Online.


Last Clue is a fairly long pursuit map. There are several buy zones that the player will encounter during the gameplay and five barriers which they would have to destroy. This map consist of two rounds, Pursuit for the first round and boss battle with Phobos for second round.

Official Description[]

2 days after receiving a distress call from the advance unit, we were deployed into the construction site. While searching the crossroads, we found advance unit commander Andrey and other advance unit members' corpses near the site.

Andrey was holding a note in his hand and he wrote about the horrible experiences he went through in this battle and also drew a map pointing to a particular area in the city. What was he trying to tell us about this location?

We increased our pace and head towards the spot indicated in the map.

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


  1. The Counter-terrorism coalition, which received a request for rescue by the advance force, dispatched a rescue force, but the advance force had already been annihilated.
  2. The rescue team finds Andrei's notebook, the last clue left by the advance team in the middle of horrific corpse. A notebook that Andrei left while dying, it contains a lot of information about the Lost City incident. Since Dr. Rex's frantic mutterings were recorded on the roof of the last battle, it became information that could lead to Dr. Rex's laboratory.
  3. The rescue team moves to Dr. Rex's laboratory, which is the area marked in the notebook, in order to find even a little bit more traces of the advance force Upon hearing that the rescue team is breaking into the lab, Dr. Rex hurriedly releases the Prototype Phobos and leaves the lab.
  4. After a fierce battle, the rescue team kills the prototype Phobos and obtains a corpse sample.
  5. CF. Prototype Phobos is the first named-type giant boss encountered. Even if it is a prototype, it is aiming for a perfect zombie that has removed all of its weaknesses, including hard skin, strong physical strength, speed and excellent combat sense formed through long term mutation.

Release Date[]

Last Clue was released on:

  • South Korea: 21 January 2010.
  • Singapore/Malaysia: 13 April 2011.
  • Indonesia: 21 December 2011.
  • CSN:Z: 23 September 2014.



  • Share your weapons with other teammates if you have powerful weapons so that all of you can proceed to the next level.
  • Help your teammates if they get overwhelmed by zombies.
  • Work in group and increase your level adequately first before proceeding to the next level.

Phobos Boss Battle[]

  • Keep moving around the map to avoid being hit by the enemies.
  • Scatter around to limit the chance of Phobos dashing multiple players and killing them at the same time.
  • It is recommended all players run in the same direction, so that player do not lead a pack of zombie into each other.
  • Be sure to eliminate Phobos as quickly as possible because strong zombies such as stalker type- psycho zombie and thrower type zombies will appear in later minutes.
    • Using powerful weapons such as Red Dragon Cannon, Magnum Launcher and M249 Phoenix will kill Phobos in under 30 seconds for normal difficulty. Under 1 minutes for hard 9 difficulty if all players wield the said weapons and focusing their attack before the zombies appear.


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.



  • Some parts of this map mirrors Hong Kong map.
  • The boss area of this map is chosen to be the tutorial map for Zombie Scenario mode. The system name for this version is zs_zombieux.
  • This is the first and only Zombie Scenario Pursuit map that has map overview.