Mutations

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

- Valve

Mutations is the name for a new set of gameplay modes scheduled to appear alongside the new campaign, The Passing in Left 4 Dead 2. The Mutations are special game modes that run for one week before it is retired, and replaced by a new Mutation each week as they become announced on the in-game Blog Post every Thursday. Presumably after all the Mutations have been revealed, a poll will be conducted once a month for players to vote for their favorite Mutation, which will return the following week. It is only available to those who have downloaded The Passing.

Revealed Mutations
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:

Realism Versus

 * You can't see each other but they can see you.

Versus Mode mixed with Realism Mode, favors Infected side

Bleed Out

 * Your health is a ticking away.

Campaign mode only, you don't have access to any med kits. You start with pills and temporary health that goes down fast. The level is full of pills and lots of random panic events.

Chainsaw Massacre

 * 4 chainsaws, millions of zombies.

Campaign Mode only, Survivors only have access to Chainsaws with unlimited fuel

Realism Versus
As Survivors

In general, as Survivors, you're going to be in a heap of trouble. If possible, try to plan out your route through the level before you leave the safe house. The fewer decisions you have to make on the fly, the better you will do. Additional safe house prep - take a melee weapon if you can. The pistols do you little to no good.

Once you are on the move, keep moving. If a teammate goes down behind you, don't stop. If they go down in front of you, only stop if there is a relative lull. You can't afford to lose a second player trying to save the first. This game will invariably come down to who is the fastest, not necessarily who is the better team. Stay together, move quick, pray.

Using microphones may be a good idea, as even Valve suggested in the in-game Blog Post for Survivors of Realism Versus to use them to communicate faster.

As Infected

Know going in that you have an immense advantage, especially if all players are human. You can see where everything is, humans, each other, etc, while the Survivors you are attacking can only see items.

Even more so than in a typical versus game, separating the Survivors is key. To this end, the Jockey is your most potent weapon. Hop on the back of someone near the back of the group, and lead them back towards the beginning of the level, away from their teammates. By the time the rest of the team notices, it'll be too late.

The Smoker also finds itself more useful than it typically is. Its ability to lurk in tough-to-shoot areas and its impressive range make it a boon for separating anyone from the pack. When used in tandem with a good Charger or Jockey, a team can be effectively crippled.

The Charger has the most potential for devastation in Realism Versus, but remains difficult to use effectively. If you, as a Charger, find yourself in a Scattering Ram-type situation, you can, with little outside help, severely hobble a team, particularly if they have already been hurt before you get to them. Not only will you be carrying and pounding one team member, your hit-stun will both do considerable damage to other survivors and render them useless long enough for you to take out the Survivor you are bashing into the ground. On top of that, they will be scattered in different directions and disoriented, leaving them primed for your fellow Special Infected to pounce.

The Hunter remains the soldier of the Infected team. He's sneaky, he's rangy, he can separate and do serious damage. Fortunately, his gameplay doesn't change much at all here. It's still jump high, pounce hard. It's possible, regardless of whether or not your teammates are good or bad, to take out an entire team as a hunter, if you play smart. Be crafty, and keep picking off the back person in the group. If you get too far away from the Survivors after killing one off, don't be afraid to hit X to jump forward -- due to frequent snarl-ups, you can almost always find a place to respawn nearby.

The Boomer and Spitter are very tough to use effectively in Realism Versus. As the Survivors are typically moving as fast as they can, you almost invariably have to be stationed in front of them. Unfortunately, this isn't very effective, because you don't often know how far ahead of them to be. Your best bet, with either, is to identify an early choke point, someplace that is the only route the Survivors can take. If you are the Boomer, lurk just past it, and either vomit as they pass, or run in and let them kill you in their midst. If you are the Spitter, find a relatively safe spot and keep your sight trained on where you know they need to walk by. Optimally, you will either catch them all or splinter the group in to two different parts, thereby making your teammates work easier.

If you happen to get a Tank (no guarantees there), be cautious you don't lose control of it. If the Survivor team realizes it is a "run for your lives" situation, don't pursue the leader. If you do, and you manage to kill or incapacitate him, you will almost certainly lose control of the tank, and that is worse than letting one guy get a bit of a head start. Your spawning teammates will take care of any front runners, the tank needs to focus on the group or the stragglers.

Room For One
As the tagline implies, only one Survivor could get on the rescue veichle, so it's an eveybody for themselves scenario. You should carry adrenaline shots so you could outrun people to the veichle. On Expert mode, you could incapacitate people by shooting them, so as soon as the rescue veichle appears, shoot everyone else and run. Also, when Hunters or Smokers attacks other players, you could run away, as less Survivors means less competition.

In Dead Center, the person who puts in the last gascan escapes. So hold on to a gascan until the second to last gascan is put in. Then run to the car and put the gascan in, so you could escape.

In The Passing, you must simply run across the bridge when it comes down, so hold on to an adrenaline shot so you could run to the car.

In Dark Carnival, the helicopter will always come to the left or right side of the stands, so stay in the middle. But be prepared, as you won't have much cover.

In Swamp Fever, stay around the gate, but don't stand in front of it, as the gate will blow apart when Virgil arrives.

In Hard Rain, Virgil will always come to the dock, so stay near there, but avoid Chargers, as they could run you into the water.

In The Parish, this is basically a race. Take the quickest shortcuts and try your best to run past the Infected to escape. You should also watch out for Smokers and Hunters, as they'll slow you down. Stay to the left as much as possible.

Within Script Files
Most of the Mutations are shown within the script files along with their game taglines:


 * Bleed Out - Your health is a ticking away.
 * Chainsaw Massacre - 4 chainsaws, millions of zombies.
 * Follow the Liter - Scavenge one can at a time.
 * Four Swordsmen - Four Swords against plenty of apocalypse!
 * Gib Fest - Blast the infected to shreds with M60s.
 * Hard Eight - Double the specials, quadruple the fun!
 * Headshot! - The only shot that counts is the one in the head.
 * Healthpackalypse! - No health in this versus game.
 * Iron Man - No respawns, no restarts, all tension.
 * Last Gnome On Earth - Protect the gnome at all cost.
 * Realism Versus - You can't see each other but they can see you.
 * Room For One - Only room for one survivor in this rescue vehicle.
 * Ultra Realism - The ultimate realistic challenge.
 * Versus Survival - Can you survive against your friends?
 * Mutation - a Mutation of Campaign mode.
 * Mutation - a Mutation of Versus mode.
 * Mutation - a Mutation of Scavenge mode.

Single-Player only Mutation modes:


 * Last Man on Earth - You will become legend to the infected as the last human left.
 * The Last Samurai – Alone, armed with only a sword you venture forth.