Scream Fortress is an anual "event" set in Valve's free to play first person shooter, Team Fortress 2. This year though, things are a little different, thanks in part to an additional co-op mode that was added over the summer. The free update includes a haunted map where random spells are cast on players, for both good and evil purposes. The two-week-long event, which starts now and ends on November 8th, will also let players cast their own spells to buff their equipment like "shifting paint colors, ghost summoning, flaming footsteps and more."
Perhaps the best addition to the update is a new spin on the Mann vs Machine co-op mode. Players will be able to battle zombies on a new map, Wave 666, against undead versions of the Heavy, Sniper, Pyro, Scout and more. There will be new achievements to earn as well.
The event and content is free and goes live today exclusively on the PC version of Team Fortress 2.
Source: Teamfortress.com