Mutation icon.png
"Each week one new Mutation is featured and the previous Mutation retired."

Mutations is the name for a set of modified gameplay modes, the first of which was released alongside the campaign, The Passing in Left 4 Dead 2. The Mutations are special game modes that were initially available for one week each before being retired, and replaced by a new Mutation each week following an announcement on the in-game Blog Post every Friday.

Periodically, a poll was conducted for players to vote for their favorite Mutation, which returned the following week as an Encore Mutation, meaning it would re-appear the next week (See below for Encore Mutations). With the download of The Passing DLC it is possible to choose what Mutation you get to play. All mutations were made freely available for play at any time on 07/24/2012.

Moreover, additional free custom Mutations created by players are available in the Steam Workshop.

Revealed Mutations[edit | edit source]

There are over 20 different Mutations planned, and playable on all Left 4 Dead 2 Campaigns.

So far, the following have been revealed on Valve's blog in the scheduled order along with their taglines:

Mutation Tagline Date(s) active Game Mode(s) Description
Realism Versus You can't see each other but they can see you. 04/22/2010 -- 04/30/2010

07/24/2012 -- ??/??/????
Versus Mode Effects of Realism Mode are added into Versus, favors Infected side due to lack of outline glows when playing as Survivors, along with stronger Common Infected. A Blog Post by Valve left it to the community to decide if Realism Versus should be a permanent feature via an online poll. On week 2, the results showed that 68% of those who took part in the poll wanted Realism Versus as a permanent game mode, which was implemented on the 21st May 2010 during the Mutation update.
Bleed Out Your health is a ticking away. 04/30/2010 -- 05/07/2010

02/25/2011 -- 03/11/2011

07/24/2012 -- ??/??/????
Campaign Mode You don't have access to any First aid kits at any time. You start with pain pills and temporary health which cannot be permanently healed. The stages will only have pills, Adrenaline and occasional defibrillators. Random panic events appear to be one step away from being permanently on, and the Special Infected spawn rate seems to be doubled.
Follow the Liter Scavenge one can at a time. 05/07/2010 -- 05/14/2010

Developer's Choice
09/10/2010 -- 09/17/2010

03/11/2011 -- 03/25/2011

07/24/2012 -- ??/??/????
Scavenge Mode The Director will spawn only one group of gas cans at a time, and until that group has been deposited into the generator, the Director will not spawn any more. If the group that spawns has more than one gas can in it the Survivors CAN pick both up so the Survivors are not necessarily limited to only picking up one gas can; they are only limited in choosing which group to go for. This mode requires everyone to stay together rather than running off to different places.
Last Gnome on Earth Protect the gnome at all costs. 05/14/2010 -- 05/21/2010

05/21/2010 -- 05/28/2010

03/25/2011 -- 04/08/2011

07/24/2012 -- ??/??/????
Campaign Mode The Survivors spawn with Gnome Chompski close by, which they must transport by carrying him all the way to the finale. The Infected will chase the Survivor carrying the gnome. The chapter will not end without the gnome being in the safe room or the rescue vehicle; thus, this mode requires the players to protect the Survivor who is holding the gnome.
Last Man on Earth You will become legend to the infected as the last human left. 05/28/2010 -- 06/04/2010

Developer's Choice
08/20/2010 -- 08/27/2010

04/08/2011 -- 04/22/2011

04/13/2012 -- 05/04/2012

07/24/2012 -- ??/??/????
Single Player Mode You will play by yourself without Survivor Bots to back you up. While there are no Common Infected, there are still the Special Infected to watch out for. If you get incapacitated from a Special Infected which grabbed you, you will automatically revive yourself, but your vision will be black and white, which means if you do not heal, you will be killed if you go down again. To balance this out, the Director orders the Special Infected to run away after incapacitation, allowing you time to recover. Defibrillators do not spawn in this mutation as there are no teammates to resurrect. There are also very few pipe bombs and no Boomers due to lacking Common Infected spawning in the campaign (though the Church Guy can still become a Boomer). Health kits spawn much more frequently than usual to help the player, especially on harder difficulties.
Chainsaw Massacre 4 chainsaws, millions of zombies. 06/04/2010 -- 06/11/2010

06/25/2010 -- 07/02/2010

Encore (Xbox 360)
08/27/2010 -- 09/03/2010

07/24/2012 -- ??/??/????
Campaign Mode Survivors start off with a default Pistol with Chainsaws on the ground. The Chainsaws have unlimited fuel. Survivors can choose between the Chainsaw or Pistol, along with picking up another Pistol dropped by another Survivor for dual-wielding. For the duration of the game, no other primary or secondary weapons will spawn. Survivor Bots, for this Mutation, will immediately pick the Chainsaw as their weapon of choice. Common Infected are active earlier and may appear right at the start of campaigns when Survivors are not ready. They are also more active in attacking Survivors due to the noise of multiple Chainsaws.
Room for One Only room for one survivor in this rescue vehicle. 06/11/2010 -- 06/18/2010

07/24/2012 -- ??/??/????
Campaign Mode Finale As the name implies, only one Survivor is allowed in the rescue vehicle. Teamplay is encouraged "only long enough until you can survive on your own" as the Blog Post states. Instead of beginning at the start of a campaign, this Mutation automatically selects the finale for everyone to start on. The first Survivor to enter the vehicle (and end the campaign) will be listed as "(Name) was the first survivor out!" in the rolling credits.
Headshot! The only shot that counts is the one in the head. 06/18/2010 -- 06/25/2010

11/18/2011 -- 12/02/2011

07/24/2012 -- ??/??/????
Campaign Mode When using guns or melee weapons, only a headshot or decapitation will kill a Common Infected. Anywhere else merely causes them to stumble. Grenades, Chainsaws, Grenade Launchers, M60s, and the Heavy Machine Gun will affect Common Infected as normal. Special Infected, remain at their default status and can be killed normally.
Versus Survival
(Survival Versus)
Can you survive against your friends? 07/02/2010 -- 07/09/2010

Encore (PC)
07/30/2010 -- 08/06/2010

Developer's Choice
09/24/2010 -- 10/05/2010

04/22/2011 -- 05/06/2011

06/03/2011 -- 06/17/2011

07/15/2011 -- 07/29/2011

08/26/2011 -- 09/09/2011

Twitter's Choice
03/29/2012 -- 04/13/2012

07/24/2012 -- ??/??/????
Versus Mode Versus Mode mixed with Survival Mode. Rounds have the teams alternating roles, trying to beat the last record set by the opposition until one team falls short of the record. Favors Infected side due to never ending waves of Common Infected and an enclosed area.
Four Swordsmen
(of the Apocalypse)
Four Swords against plenty of apocalypse! 07/09/2010 -- 07/16/2010

Encore (Xbox 360)
07/30/2010 -- 08/06/2010

Twitter Choice
03/16/2012 -- 03/29/2012

07/24/2012 -- ??/??/????
Campaign Mode The Survivors will start with a Katana in hand from the start; primary weapons and other secondary weapons won't spawn. Common Infected do not spawn; only Special Infected do, albeit at an increased spawn rate. The title is probably a reference to the four horsemen of the Apocalypse.
Hard Eight Double the specials, quadruple the fun! 07/16/2010 -- 07/23/2010

Developer's Choice
09/03/2010 -- 09/10/2010

12/03/2010 -- 12/17/2010

02/03/2012 -- 02/24/2012

07/24/2012 -- ??/??/????
Campaign Mode The maximum number of Special Infected spawning at the same time has been raised from four to eight. Additionally, the spawning rate of Special Infected has been increased.
Healthpackalypse! No health in this versus game. 07/23/2010 -- 07/30/2010

Developer's Choice
09/17/2010 -- 09/24/2010

09/23/2011 -- 10/07/2011

07/24/2012 -- ??/??/????
Versus Mode As the tagline implies, there will be no first aid kits, pain pills, or Adrenaline Shots in this mode. Survivors must be extremely careful, especially against the human-controlled Special Infected as there is no way to recover health once it is lost. Favors Infected side due to no ability to recover lost health.
Gib Fest Blast infected to shreds with the M60. 08/06/2010 -- 08/13/2010

Encore (PC)
08/27/2010 -- 09/03/2010

11/19/2010 -- 12/03/2010

05/20/2011 -- 06/03/2011

10/07/2011 -- 10/21/2011

01/13/2012 -- 02/03/2012

07/24/2012 -- ??/??/????
Campaign Mode The Survivors will start with M60s and a Magnum to fend off the Infected. No other primary or secondary weapons will spawn during the game. The M60s will have unlimited ammunition similar to Chainsaw Massacre mode. Incendiary and explosive ammo are both limited to 150 rounds, after which the M60 reverts to 150 unlimited rounds.
Iron Man No respawns, no restarts, no ammo, only tension. 08/13/2010 -- 08/20/2010

10/21/2011 -- 11/04/2011

07/24/2012 -- ??/??/????
Realism Mode Once a Survivor dies, they can only come back with a defibrillator, if found, or if the team makes it to the safe room. If all the human Survivors in a team die, they must start all over from the lobby. There are no ammo piles throughout the whole campaign, so the only way to get more ammo is to change your gun. This Mutation is almost the same as Realism (no Survivor or item glows, Common Infected are tougher, etc.), with only the penalty of the game ending when everyone dies instead of restarting the chapter.
Taaannnkk! Every Special Infected in this Versus game is a Tank! 10/05/2010 -- 10/15/2010

11/12/2010 -- 11/19/2010

05/06/2011 -- 05/20/2011

07/29/2011 -- 08/12/2011

02/24/2012 -- 03/16/2012

07/24/2012 -- ??/??/????
Versus Mode The Special Infected team will only spawn as Tanks throughout this Mutation. If a Tank dies, the player will respawn as another Tank. Survivors get a 15-second head-start, but first aid kits have been replaced by pain pills. This Mutation was revealed on the Left 4 Dead Blog as part of The Sacrifice weekend updates, and activated on a Tuesday instead of Fridays as normal to celebrate the release of The Sacrifice.
Hunting Party Nothing but Hunters on the prowl. 10/15/2010 -- 10/22/2010

06/17/2011 -- 07/01/2011

09/09/2011 -- 09/23/2011

07/24/2012 -- ??/??/????
Campaign Mode The Special Infected in this campaign are only Hunters. Boomers, Smokers, Jockeys, Chargers and Spitters do not spawn. Up to six Hunters can be present at once. Tanks and Witches will still spawn as normal, including specially scripted ones (The Riverbank and The Docks, along with finales).
Lone Gunman You and your Magnum against the deadly horde and Boomers. 10/22/2010 -- 10/29/2010

07/01/2011 -- 07/15/2011

07/24/2012 -- ??/??/????
Single Player Mode You will play by yourself with no Survivor Bots to back you up, and armed with only a Magnum. While other weapons do not spawn, grenades still do. The only Infected are Boomers and the Horde. Tanks and Witches will still spawn as normal, including specially scripted ones. Common and Uncommon Infected will hit a lot harder; each hit from the front will do 15 damage on Easy, 30 damage on Normal, 75 damage on Advanced and instant incapacitation on Expert.
Bleed Out Versus Now you have a good excuse for rushing through Versus. 10/29/2010 -- 11/05/2010

07/15/2011 -- 07/29/2011

07/24/2012 -- ??/??/????
Versus Mode Bleed Out Versus is Versus Mode with Bleed Out rules. Survivors will only have temporary health throughout the game, with only Adrenaline Shots and pain pills spawning instead of first aid kits.
Healing Gnome Share the gnome to replenish life. 11/05/2010 -- 11/12/2010

08/12/2011 -- 08/26/2011

07/24/2012 -- ??/??/????
Campaign Mode Gnome Chompski spawns with the Survivors. All Survivors start with 99 temporary health. No healing items of any kind will spawn. As the only method of healing is to carry Gnome Chompski, Survivors must alternate in carrying the gnome to restore their health.
Special Delivery These specials deliver non-stop action. 12/17/2010 -- 12/31/2010

07/24/2012 -- ??/??/????
Campaign Mode A variation of Hard Eight, with the maximum number of Special Infected raised from four to eight. Additionally, the spawn timer of Special Infected has been removed. To offset the larger number of Special Infected, Common Infected along with Uncommon Infected do not spawn. Special Delivery is the first community Mutation officially released for both PC and Xbox 360, created by Rayman1103 from his custom Mutations mod.
Flu Season The smell of bile and spit in the air. 12/31/2010 -- 01/14/2011

05/25/2012 -- 06/14/2012

07/24/2012 -- ??/??/????
Campaign Mode In this mode, only Boomers and Spitters spawn normally. Common Infected are spawned by the Boomer's bile (if it lands on Survivors) or during Crescendo Events. Tanks and Witches only spawn during scripted events depending on the campaign. Boomer and Spitter spawn timers have been removed and maximum number raised from four to ten. Boomers are much faster and more agile, and do not have cooldown on their bile vomit, while Spitters are also faster and more agile with shorter cooldown on their acid spit. Flu Season is the second community Mutation officially released for both PC and Xbox 360, and is a combination of the works of SR69MMJC and Karma Jockey.
Riding My Survivor Do I hear a Jockey? 01/14/2011 -- 01/28/2011

07/24/2012 -- ??/??/????
Versus Mode Only Jockeys spawn in this mode. Jockeys have increased health, damage, and speed. Riding My Survivor is the third community Mutation officially released for both PC and Xbox 360, created by Winded.
Nightmare You'll never see them coming! 01/28/2011 -- 02/11/2011

06/15/2012 -- 07/10/12

07/24/2012 -- ??/??/????
Survival Mode In this mode, Common Infected and Special Infected are stronger. Survivors will be unable to see glows on fellow players or objects. The fog is adjusted to be thicker on all survival levels. Nightmare is the fourth community Mutation officially released for both PC and Xbox 360, inspired by Karma Jockey.
Death's Door You go down, you're dead. 02/11/2011 -- 02/25/2011

07/24/2012 -- ??/??/????
Campaign Mode In this mode, incapacitation is disabled. If a Survivor falls, they will die instantly. First aid kits do not spawn; pain pills will spawn where they would normally spawn, such as in safe rooms and finales. Death's Door is the fifth community Mutation officially released for both PC and Xbox, created by Rayman1103.
Confogl For the competitive type. 11/04/2011 -- 11/18/2011

12/02/2011 -- 01/13/2012

07/10/2012 -- 07/24/2012

07/24/2012 -- ??/??/????
Versus Mode In this mode, players start with pain pills in their inventory, and can find additional pills and adrenaline in each map, but no first aid kits spawn anywhere. In addition, the only primary weapons available are Tier 1 weapons and the Hunting Rifle. Confogl is the sixth community Mutation officially released for both PC and Xbox, created by ProdigySim.
Holdout Custom


In this mode, players will hold out in a certain location until rescue arrives, against multiple waves of zombies.. It has two modes: 'Training' and 'Challenge'. In training, you hold out against a certain amount of waves, with a helicopter delivering supplies about halfway through. In challenge, you must fuel a generator to make a timer count down, with the helicopter arriving the wave after it finishes. In holdout, special infected drop 'supplies', which can be used to buy items such as Defibrillators or Tier 2 weapons, as well as custom weapons such as mines.
Dash Custom Mode In this mode, players must move between different waypoints, with a horde and Specials spawning after each waypoint is activated. Waypoints either are activated by one player, or require all four players to activate.
ShootZones Custom Mode In this mode, players must stand in specific 'shootzones' (gravestones) in order to deal damage. When in a shootzone, it will play music. After several seconds, the shootzone will be disabled. Only Common Infected spawn on this mode.
L4D1 Coop Campaign Mode In this mode, only Left 4 Dead weapons, items and Special infected spawn. This means only Smokers, Male Boomers and Hunters, along with Witches and Tanks will spawn as special infected. The weapons that spawn include the Pump Shotgun, Tactical Shotgun and Submachine Gun with their ammo changed to their original amounts, as well as the Assault Rifle and Hunting Rifle, and Pistols as the only secondary. It is unknown if the shotguns have their pellet damage changed. The only items that spawn are Pipe Bombs, Molotovs, Health Kits and Pills. Map-based items such as Fireworks are unaffected, as well as Uncommon Infected.
L4D1 Versus Versus Mode Identical to L4D1 Coop, but in Versus Mode instead.

Console Commands[edit | edit source]

To play any Mutation without it being up for that week on the PC version of Left 4 Dead 2, activate the console and type in:

map map filename mutation-name

The map filename is any of the maps in the game, or a custom map.

Replace mutation-name with a command from below:

Command Mutation
mutation1 Last Man On Earth
mutation2 Headshot!
mutation3 Bleed Out
mutation4 Hard Eight
mutation5 Four Swordsmen
mutation6 Nothing
mutation7 Chainsaw Massacre
hardcore Ironman
mutation9 Last Gnome On Earth
mutation10 Room For One
nohealthversus Healthpackalypse!
mutation12 Realism Versus
mutation13 Follow the Liter
m60s Gib Fest
mutation15 Versus Survival
mutation16 Hunting Party
mutation17 Lone Gunman
mutation18 Bleed Out Versus
mutation19 Taaannnkk!
mutation20 Healing Gnome
community1 Special Delivery
community2 Flu Season
community3 Riding My Survivor
community4 Nightmare
community5 Death's Door
community6 Confogl
gunbrain GunBrain
l4d1coop Left 4 Dead 1 Coop
l4d1vs Left 4 Dead 1 Versus
holdout Holdout
dash Dash
shootzones Shootzones

So, for example, to play Dead Center with the Ironman Mutation, type into the console:

map c1m1_hotel mutation8

A menu mod exists that simplifies this, as well as enabling lobbies.[1]

Note: You cannot play multiplayer using this method.

Unrevealed Mutations[edit | edit source]

Future content.png "Ain't seen anything like this before..."
This article contains new or upcoming content, and therefore may be incorrect and will change from time to time.

WARNING: Spoilers.

The following were found in a Steam-Group announcement and have not been seen in a schedule as of yet. They can also be found amongst the game's script files. As they have not been announced by Valve yet, they may still be subject to changes or removal.

Mutation Tagline Game Mode(s) Description
The Last Samurai Alone, armed only with a sword, you venture forth. Single Player Mode You are alone with no Bots to back you up, similar to Last Man On Earth. However, you will only be armed with a Katana. Common Infected do not spawn; only Special Infected do.
Ultra Realism The ultimate realistic challenge. Realism Mode There is/are no HUD or outlines around to help you here, according to a video. Enemy Infected changes are unknown, but may have more resistance to gunfire similar to normal Realism Mode.
VIP Target Unknown Versus Mode Last Gnome on Earth mixed with Versus Mode. The Survivors start with Gnome Chompski nearby and must transport it to each safe room and into the rescue vehicle during the finale. Favors Infected side due to Common Infected constantly harassing the gnome carrier who cannot use weapons while carrying, effectively putting one Survivor out of play.

Strategies[edit | edit source]

Realism Versus[edit | edit source]

Bleed Out[edit | edit source]

Follow the Liter[edit | edit source]

Last Gnome on Earth[edit | edit source]

Last Man on Earth[edit | edit source]

Chainsaw Massacre[edit | edit source]

Room for One[edit | edit source]

Headshot![edit | edit source]

Versus Survival[edit | edit source]

Four Swordsmen[edit | edit source]

Hard Eight[edit | edit source]

Special Delivery[edit | edit source]

Healthpackalypse![edit | edit source]

Gib Fest[edit | edit source]

Iron Man[edit | edit source]

Taaannnkk![edit | edit source]

Hunting Party[edit | edit source]

Lone Gunman[edit | edit source]

Healing Gnome[edit | edit source]

Flu Season[edit | edit source]

Encores and Developer's Choice[edit | edit source]

In 2010, after every four or five weeks, Valve would announce an encore week in which the community vote for a Mutation to be replayed. Only recent Mutations that have been played may be voted for. Alternatively, the developers would choose to replay one of their chosen Mutations for a week as a "Developer's Choice". The following encore weeks re-showcased the following Mutations:

  • Friday, May 21st (week 5) had Last Gnome on Earth return for another week.
  • Friday, June 25th (week 10) had Chainsaw Massacre reappear. On the Xbox 360, it led with 43% of the votes. However it was much more close on the PC. Chainsaw Massacre won by 1%, specifically 500 more votes, than the second most voted PC Mutation: Headshot!.
  • Friday, July 30th (week 15) had a split vote. For the PC, Versus Survival won by 6% more than Four Swordsmen. However, on the Xbox 360, Four Swordsmen won by 10% more than Versus Survival.
  • Friday, August 20th (week 18) had developers choosing Last Man On Earth to be replayed for one week on both PC and Xbox 360.
  • Friday, August 27th (week 19) had a split vote. For the PC, Gib Fest won by 5% more than Versus Survival. However, on the Xbox 360, Chainsaw Massacre won by 5% more than Gib Fest.
  • Friday, September 3rd (week 20) had developers choosing Hard Eight to be replayed for one week on both PC and Xbox 360.
  • Friday, September 10th (week 21) had developers choosing Follow The Liter to be replayed for one week on both PC and Xbox 360.
  • Friday, September 17th (week 22) had developers choosing Healthpackalypse! to be replayed for one week on both PC and Xbox 360.
  • Friday, September 24th (week 23) had developers choosing Versus Survival to be replayed for two weeks on both PC and Xbox 360, as the team will be busy 'working on their infrastructure'.
  • Friday, November 12th had Taaannnkk! reappear out of the five new Mutations, leading with an overwhelming majority vote of 51% on Xbox 360 (second highest vote was Hunting Party with 17%), and 47% on PC (second highest was Healing Gnome with 17%).

Achievements & Awards[edit | edit source]

Gnome.png GNOME (0G)
Unlock the Gnome by playing any 6 Mutations.

Mutant-Overloard.gif MUTANT OVERLORD (30G)
Play 6 Mutations.

Notes[edit | edit source]

  • Week 2 of the In-Game blog made a poll, asking if Realism Versus should have a permanent slot in the game modes. Due to majority votes, Realism Versus is now a permanent game mode.
  • The Mutation Bleed Out was previously bugged, as on The Passing, the original Survivors would sometimes throw first aid kits down to the new Survivors during the finale The Port. Although this was quickly patched by Valve in the 30th April update, the bug is still currently active on the Xbox 360 version of Left 4 Dead 2.
    • Furthermore, if in a black and white state after being incapacitated, taking pain pills will return color, but the heartbeat (signifying emergency state on Third Strike) can still be heard.
  • The Mutation Last Gnome on Earth may be slightly buggy. When you play Dark Carnival, on the second chapter, you can obtain a second Gnome Chompski from the shooting gallery and progress through the whole campaign with two gnomes, who are treated the same as each other (Common and Uncommon Infected will equally go after the gnome carriers), yet when on your last "life" i.e. seeing in monochrome, only one of these will be outlined. This has yet to be patched, if it is a bug.
    • Getting any gnome into the rescue vehicle counts for the Guardin' Gnome achievement if not obtained already. You can even start the game at The Concert, then play through to get this achievement.
    • When you are playing Dead Center on the the first chapter, make sure you hold the gnome in the elevator, if not he will fall right through the floor and become unreachable.
    • This can also happen on the ferry on Swamp Fever, as the gnome falls through the wood and lands in the insta-kill water.
  • In the Mutation Last Man on Earth, the guns in Whitaker's Gunshop are different. Where the Pump Shotguns and Submachine Guns usually are, their Tier 2 replacements will occupy their space instead.
    • In the Atrium after you have finished pouring the gas cans and escaped, the Common Infected appear outside.
    • It is possible to play The Sacrifice in Last Man on Earth. However, this makes the finale rather illogical, because at the end you still sacrifice yourself, which doesn't save anyone.
    • Many of the cutscenes are messed up because the other Survivors are not there to act or speak their lines.
    • You are not exactly the "Last Man on Earth", since the rescuers are still heard talking through the radios in some campaigns. The drivers of the rescue vehicles still can be seen.
  • In the Mutation Chainsaw Massacre, on The Passing's finale the original Survivors will be using Pistols instead of their normal Tier 2 weapons. Louis, however, continues to use the Heavy Machine Gun.
    • This mode is currently bugged. Similar to the Bleed Out Mutation bug during The Passing on the finale (see above note), the original Survivors may occasionally throw down Tier 2 weapons (including the M60) to the new Survivors during the finale The Port, letting Survivors fight with a Chainsaw and firearm.
    • During this Mutation it is possible to find other primary weapons in the campaign - for example in Hard Rain's second stage Sugar Mill, at the safe room where the diesel gas cans are, there is a single Pump Shotgun on the ground. As the gun is loaded to its maximum capacity, it can serve as a backup weapon for dealing with Boomers and Spitters. As the Mutation is meant to be revolved around using the Chainsaw or Pistols you begin with (since no firearms or ammo piles spawn generally), this is a bug.
    • Laser sights will still spawn in this mode, but they are unusable since you have no primary weapons. The only exceptions are when you obtain a primary weapon via the bugs described above.
  • In the Mutation Room for One, playing the whole finale will get you the campaign achievement if you don't have it. Even if you're not the one to make it into the rescue vehicle, you will still get the achievement as long as you are alive when the campaign ends. For example, making it into the Dark Carnival helicopter, and getting MIDNIGHT RIDER.
    • In the Hard Rain finale, Town Escape, if a Survivor jumps from the flat level dock and not the inclined ramp onto the boat, that Survivor will live but NOT be counted as the winner. The Survivor that jumps from the inclined ramp is the winner even though the ending animation might show otherwise. This may be a bug.
  • In the Mutation Headshot!, it is possible to decapitate a Common Infected and they will still be standing. This is shown much more often if you headshot them.
    • When incapacitated, shooting Common Infected anywhere translates into an instant headshot, so fending yourself when incapacitated is actually easier.
    • When a Common Infected is killed with a Frying Pan or Nightstick, it doesn't lose its head.
    • Riot Infected are extremely hard to kill in this Mutation as they have to be shot/decapitated from the back of the head.
    • The update for the Mutation Headshot! has not been obtainable by a lot of Xbox 360 owners of the game (if not hooked up by LAN connection to their modem). After they start up the game and get to the main menu, the Blog Post from week 1 of Mutations will be shown there, and Realism Versus will not have its usual permanent slot, but it will be available under the Mutation slot. Reasons for this are so far unknown, though it's most likely due to a bug or the connection to the servers. Additionally, the date of the Blog Post will say March 23rd, 2010, despite that the original date of The Passing's official released date was on April 22nd, 2010.
  • In the Mutation Four Swordsmen, unlike Chainsaw Massacre, Survivors immediately start the campaign with Katanas in hand. However, the cutscene played at the start of each campaign was designed for the Survivors to have the Pistol in their hands, so there may be some slight animation errors in how they hold the Katana with their pistol grips. This is immediately fixed as soon as players control the Survivors, as they will hold the Katana normally afterwards. Also, if killed and revived from a closet, you will start with a pistol, likewise if a Survivor dies and re-appears in the safe room.
    • The Mutation Four Swordsmen appears as that name in the Mutation in-game option, but on the update and Blog Post (in-game as well as website blog), the Mutation is known by the longer name Four Swordsmen of the Apocalypse. It is unknown why Valve chose to use longer and shorter variations of the Mutation's name rather than sticking with one single name.
    • On Swamp Fever, at The Swamp, just after the hanging military man in the trees, a Magnum and a Katana can be found at the small wooden dock. If Survivors wish to break the theme of 'swords only', the Magnum can be handy for dealing with Special Infected at range. As the Katana is meant to be the only weapon for use in this Mutation, this is considered to be a bug.
    • Similar to Chainsaw Massacre, it is possible to find other primary weapons in the campaign - for example in Hard Rain's second stage Sugar Mill, at the safe room where the diesel gas cans are, there is a single Pump Shotgun on the ground. As the gun is loaded to its maximum capacity, it can serve as a backup weapon for dealing with Special Infected from a distance, or for killing Witches by cr0wning them. As this Mutation is meant to be revolved around using only the Katana, this is a bug.
    • Laser sights will still spawn in this mode, but they are unusable since you have no primary weapons. The only exceptions are when you obtain a primary weapon via the bugs described above.
  • In the Mutation Gib Fest, during The Passing, the original Survivors are still capable of dropping laser-sighted M60s. Though the M60 drop itself is pointless, it's still useful for its laser sight (given that the Survivors have not obtained laser sights beforehand).
    • Also, in some campaigns (though rarely) like the Left 4 Dead 2 port of Death Toll or Cold Stream Tier 2 weapons may still spawn. Such as one-Combat Shotguns at the beginning of South Pine Stream or Auto Shotguns during the escape from the Sugar Mill.
    • It is possible, but extremely rare, to find a Grenade Launcher in certain Gib Fest Campaigns. As the Grenade Launcher was ever only coded to have one shot per magazine, this results in the grenade launcher having almost no cooldown between shots (it can fire as soon as the coding for infinite ammo kicks in and replaces its expended shot).
    • The inverse can happen when playing on Cold Stream. The players and bots will spawn with their standard weapons, and may get a choice between a submachine gun variant and a pump shotgun variant, with a few secondary weapons spawning nearby. However survivors will not get access to the M60, even if killed and revived. It is possible that the above glitch may happen and spawn a M60 or a Grenade Launcher in certain areas.
    • Similar to Chainsaw Massacre and Four Swordsmen, it is possible to find other primary weapons - for example in Hard Rain's second stage Sugar Mill, at the safe room where the diesel gas cans are, there is a single Pump Shotgun on the ground. As this gun has unlimited ammunition too, it can serve as a replacement for the M60. As this Mutation is meant to be revolved around using only M60's and Magnums, this is a bug. Bots are automatically pick up the shotgun as their programming forces them to discard the M60, Chainsaw and Grenade Launcher immediately if possible.
  • In the Mutation Iron Man, it is still possible to find, and also use, Defibrillators. Though this Mutation states that once you die, you're dead permanently, and yet there are still Defibrillators that you can find and use, this might be a bug, but is not completely certain, as the Mutation is based on Realism rules, which allow Defibrillators to revive Survivors.
    • The in-game tagline description of the Mutation Iron Man does not mention "no ammo". It just states no respawns, no restarts, all tension, unlike the Blog Post (in-game and web blog) which states no respawns, no restarts, no ammo, all tension.
    • The in-game tagline description of the Mutation Iron Man says that there are no respawns and yet after Survivors make it to the safe room, all dead Survivors are respawned. This may either be for gameplay balance or a bug.
  • The Mutation Versus Survival has also been addressed officially by Valve in the blog as Survival Versus. It is unclear which name has overall precedence, as Valve makes use of both names. The Mutation name as it appears when selecting the game mode, however, is Versus Survival.
  • The Mutation Taaannnkk! has also been addressed officially by Valve in the blog as TAAANNNKK!! (in all capital letters and two exclamation marks), as well as Taaannnkk!! (with two exclamation marks instead of one). It is unclear which name has overall precedence, as Valve makes use of all three names. The Mutation name as it appears when selecting the game mode, however, is Taaannnkk!.
    • Sometimes, Tank players may spawn in an area where it is impossible for them to reach the Survivors due to no climbable walls. This is a bug.
    • Tanks spawn with half the amount of health they would normally get in a Versus game (3000 instead of 6000). This is to balance the number of simultaneous Tanks, giving the Survivors a small chance of survival.
    • Tank spawns can sometimes be unfortunate to the Survivors as it is possible for Tanks to spawn in the same general area (room, hallway, safe room, etc.). It is possible that Tank spawns are based on the line of sight of the survivors. This can be deadly to players who are not familiar with The Apartment of No Mercy as it is possible for Tanks to spawn directly by a Survivor.
    • Unlike Versus mode, this Mutation only spawns Tanks equal to the amount of players on the Infected team.
    • Despite the description saying "Every Special Infected in this Versus game is a Tank!", Witches can still spawn which may be unfortunate for the Survivors if one spawns in their path.
  • In the Mutation Hunting Party, Tanks and Witches will still spawn.
  • In the Mutation Lone Gunman, items such as Laser sights, Defibrillators, ammo upgrades, an extra magnum, and ammo piles will spawn even if they cannot not be used.
    • Despite the tagline saying only the horde and Boomers spawning, Tanks and Witches will still spawn.
    • On The Sacrifice at Port Finale, the final generator still has to be restarted, but due to the nature of the Mutation, nobody needs to be left on the bridge in order to restart the generator to complete the campaign.
    • The picture for Lone Gunman has an Beretta 92, yet there is no Beretta 92 in the game.
  • In Hard Eight mutation, there's a rare chance where Survivor Bots will pick up a melee weapon, unlike normal campaign where they'll only use pistols.
  • In the Mutation Healing Gnome, as the Survivor Bots cannot hold throwable items, they will have no methods of healing.
    • As can be seen in this video at about five minutes and forty-eight seconds, in Swamp Fever's Plank Country, you can shoot a gnome off of the sign allowing you to have two gnomes.
  • In the Mutation Last Man on Earth, despite the mutation only allowing you to be incapacitated once without First Aid, the gamemodes.txt file doesn't have "sv_max_incapacitated_count" set to "1".
  • Some of the Mutation names along with their taglines appear to be based on certain themes, imagery, or others:
    • Chainsaw Massacre is likely a reference to The Texas Chainsaw Massacre franchise.
    • Iron Man is likely derived from the Ironman Triathlon, in terms of how grueling the mode will be (Ironman Triathlons have a mantra where "just finishing is a victory"). A number of other games, such as Halo 3, also have modes based on the name.
    • Four Swordsmen (along with its longer name Four Swordsmen of the Apocalypse), along with its tagline Four Swords against plenty of apocalypse!, is a play on the Four Horsemen of the Apocalypse from the last book of the New Testament of the Bible. It could also be a reference to The Legend of Zelda: Four Swords, though this is unlikely.
    • Last Man on Earth, along with its tagline You will become legend to the infected as the last human left., is a reference to the novel I Am Legend and its related film adaptations, where the protagonist is (what he believes) the last surviving human in a world full of infected beings (in this case, vampires, who he quickly becomes a legendary monster to). The title is derived from the Italian movie The Last Man on Earth (L'ultimo uomo della Terra), which was based on the I Am Legend novel.
      • With the infected beings in the novel and film adaptations being vampires, this might also lead into Francis' mistaken belief that the Infected are vampires due to their similar behavior, aggression, and running speed, in comparison to stereotypical film zombies which move at a lumbering pace.
        • The name of the mutation may also be based on Zoey's cut line from the old versions of the Left 4 Dead intro, where Bill would wipe the puke off on Francis's vest after being asked if she's interested in Francis's "improvement".
    • Bleed Out is a colloquial term for exsanguination, the fatal process of total blood loss. It is more commonly known as "bleeding to death". It is also a reference to a Survivor bleeding out to death if left incapacitated for too long.
    • The Last Samurai may be named after the movie of the same name, where the protagonist is armed with just a sword against superior odds. The protagonist in the movie, however, was only alone in terms of racial group.
    • Flu Season takes the two Special Infected whose special attacks are analogous with the biological illnesses associated with the flu (in this case, vomiting). Along with the timing, "flu season" is commonly associated with winter, which is when the Mutation happened to take place.
  • Some achievements may be easier to earn on some Mutations. Examples include:
  • Although Realism Versus has become a permanent game mode, playing it counts towards the MUTANT OVERLORD achievement, if not already obtained.
  • Even on a Mutation that excludes Common Infected, they can occasionally be seen milling about idly on various stages. Additionally, custom campaigns that force Common Infected spawns will still result in encountering aggressive groups of them in these Mutations.
  • Chainsaw Massacre, Versus Survival, and Gib Fest are currently the most repeated Mutations, having appeared three times altogether as of November 19th 2010. Chainsaw Massacre and Gib Fest have returned via encores, while Versus Survival has returned via Developer's Choice and an encore.
  • The mutation Special Delivery was previously bugged. If a player played the mutation with bot-controlled Srvivors, sometimes the bots may disappear completely. This would remove the in-game character, the health meter at the bottom of the screen and the health meter in the side menu for the remainder of the campaign. Since then Valve has fixed it in the community1.nuc file, preventing this bug from ever happening again.
  • In the Death's Door mutation, completing The Sacrifice alone is impossible since the game restarts as soon as the player restarts the Generator instead of displaying end credits due to the fact that incapacitation is disabled in this mutation.

Gallery[edit | edit source]

Videos[edit | edit source]

Videos Walkthroughs.

Single/Co-op Mutations:

Versus Mutations:

Older Videos:

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