We haven't heard much about Killing Floor lately but the creature co-op-themed shooter is going to get all merry and jolly starting next week. Developer-publisher Tripwire Interactive has just announced plans to hold its first ever Twisted Christmas event in the game which will last from December 14 to January 4.

The free event includes a new level, Santa's Evil Lair, along with all of the creatures in the game replaced with holiday-themed versions of themselves (they go there with the Nutpound). Plus there will be 13 new Christmas achievements added as well as a new difficulty level, Hell on Earth. If you managed to get 10 of them you can get a new playable character, Baddest Santa. Finally there's a Team Fortress 2 crossover. Anyone who owns both games can get the red and blue Pyro character to use in Killing Floor.

In addition to the free Twisted Christmas event, a new paid DLC for the game will be released next week. London's Finest will add four new playable characters with a UK twist to the game. Pricing was not announced. You can check out a video of what you can expect from Twisted Christmas after the jump: