The Halloween event is that time of the year when enchantments, hauntings, and family curses fall upon the world-wide facilities of Mann Co., and, for several days in October and November, Team Fortress 2 is transformed into Scream Fortress! First introduced in the The Terrifying Team Fortress Haunted Hallowe'en Special of 2009, Halloween events feature activation of Halloween-themed start screens, spooky sound cues, haunted maps, soul-harvesting contract campaigns, scary or ridiculous Halloween cosmetics, Ghosts, and monsters, with Scream Fortress Patches adding new Halloween content.
Halloween events have typically opened with a Major Update content patch and concluded with removal of Halloween effects 10 or more days later. With the 2019 event, an in-game announcement was made signaling the beginning of Halloween celebrations on October 2nd with a promise of new Halloween content, which was released in a Patch eight days later.
Most of the individual Halloween Updates introduced new features of the Halloween event celebration, whether new maps, monsters, or mechanics, like magic spells or the Soul Gargoyle. Valve treated the first seven Halloween events as "major updates", each with an update page on the official Team Fortress website and a comic of some form. However, from the 8th annual event onward, no update pages or comics were published. From the beginning, Halloween events have been linked with continuations of the Team Fortress 2 Storyline, with the release of Zephaniah Mann's last will and testament and family portrait and the coupling of the Halloween comics with closely released main Storyline comics, notably the murders of Blutarch and Redmond and the crossovers of Merasmus.
While the first six events released seven haunted maps (all but two developed by Valve) the next three events released 12 quality Community haunted maps. Another consideration is that the Halloween events of 2016, 2017, and 2018 released far fewer cosmetic items. The 2017 Halloween event was so minimal as to have no maps, no comic, and only one cosmetic item; however, it can be noted that that particular 2017 Halloween event (and that event's single item) was integrated with the then ongoing massive Jungle Inferno Campaign that introduced a new Contract system, with coordinated new Halloween Contracts. Later events resumed introduction of new haunted maps and cosmetics, with the Halloween cosmetics distributed through the now unfarmable Contracts.
List of Halloween events