While Valve has remained rather quiet regarding Left 4 Dead 2's new multiplayer mode, the developer took the wraps off it tonight at a press event in San Francisco. Dubbed "Scavenge," the mode essentially combines Left 4 Dead's Versus and Survival modes. One team, the survivors, is tasked with retrieving scattered gas canisters and using them to fill up generators. As in Versus, the other team takes control of "special infected" and attempts to stop the survivors alongside legions of regular zombies.

A total of 16 gas cans appear every round--the goal is to use as many of those cans as possible within the time limit. Each round kicks off with a ticking 120 second timer, and every gas can used adds another 20 seconds to the clock. As the canisters are a limited commodity, survivors have to be careful that they don't shoot them or otherwise cause them to explode. And they'll also have to watch out for the other team too, as enemies can detonate the canisters at points. One match is comprised of three rounds, with each team getting a shot at the Survivor side in an attempt to collect the most gas cans. The team that wins two out of three rounds triumphs overall. If there is a tie in the number of gas cans used in a particular round, the side with the lowest recorded time gets the tally. Six "Scavenge" maps will be including with Left 4 Dead 2 when it comes to PC and Xbox 360 on November 17, alongside the game's other co-op and competitive modes.