The custom map is Helltower, where the Red and Blu teams must each push their own respective cart through enemy territory to an end goal, just like in any traditional Payload Race match. This isn't the usual Payload Race, however, because on this map players can equip a spell book to their action slot, which allows them to pick up and cast various spells throughout the match. There's also a custom event called The Witching Hour - a path appears for each team leading to the base of the in-map clocktower, where players can grab a rare spell and teleport back to their spawn room with enhanced health and speed buffs.
The update also adds over 100 new items for dress-up (turn the Scout into a terrier or give the Pyro a nice Goldilocks wig) and eight new holiday-themed achievements. In order to grab the update, simply head into Steam and boot up Team Fortress 2 for the mandatory install.