Mutations are exclusively available to owners of 'The Passing' DLC. There are over 20 Mutations planned, each playable on all L4D2 Campaigns.
The Passing also introduces a series of weekly game mode events dubbed 'Mutations.' These week-long runs of new gameplay modes range from 'Realism Versus' mode to 'Chainsaw Massacre,' which gives all players chainsaws with an unlimited supply of gasoline.
The first game add-on for Left 4 Dead 2 brings the original Left 4 Dead (L4D1) Survivors down south for a meeting with the L4D2 cast, while delivering new single-player, multiplayer and co-operative gameplay for the PC and Xbox 360.
