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:

Unrevealed Mutations
The following were found in a Steam-Group annoucement and have not been seen in a schedule as of yet. As they have not been announced by Valve yet, they may still be subject to changes or removal.

There are four more Mutations, but nothing more is known about them. The mode that they will be used in, however, has been confirmed. There are:


 * 2 More Mutations for Campaign Mode.
 * 1 More Mutation for Versus Mode.
 * 1 More Mutation for Scavenge Mode.