Last week, Valve reactivated TF2's five previous Halloween parties, and now the main event—the sixth—has gone live. Scream Fortress 6 adds a spooky carnival map, an evil hypnowizard controlling it, plenty of Halloween gear and achievements, oh and bumper cars, because why not. You have until the 12th of November to make the most of it, at which point TF2 will return to its regular, sadly bumperless self.
The new Carnival map is based on Doomsday, and contains a cornucopia of activities seen over by the wizard Merasmus. If you're wondering why you're fighting those dastardly blue/red guys there, you'll want to read the event's prequel comic. To cut a long story short: Merasmus forgot to build his carnival on top of an ancient burial ground, so he's hoping to create one with our corpses. A strongman, spells, curses, copious amounts of urine, and bumper cars feature heavily in his plan.
Valve have made big changes to the way gifts work in this latest Halloween event: you'll now receive a bag of items just for logging in, with the chance to earn a second during the event. You can read the reasoning behind this decision here, but it's basically an attempt to inject some fun back into proceedings.
For more information, check out this poster for the event, or, y'know, log in to Team Fortress 2.