Every year around this time, the light-hearted (albeit bloody) world of Team Fortress 2 gets a little bit darker. Past years have brought a horseless headless horseman and Demonman. The fourth annual "Scream Fortress" update brings a necromancer with a grudge and some magic potions in tow.

The update goes live today and lasts through November 8. As usual, it ties into a new comic that plays with the premise. The magician Merasmus will enter haunted King of the Hill maps to terrorize your crew, throwing bombs and booby-trapping the control points. Each time a point changes hands, a random effect will trigger some "horrible fate." Or possibly something good, but you know, more likely the horrible fate thing.

You'll also randomly find spells that you can cast on items in your backpack, giving them magical effects like ghost summoning or flaming footsteps, or more modest ones like repainting your items. One spell promises to make you an evil sorcerer.

The new "Wave 666" replaces your usual Machine co-op opponents with brain-hungry zombies, and you can score two new achievements -- one for beating Merasmus, and one for getting to Skull Island.