Every year you can count on Tripwire to crank out some content for Killing Floor for Christmas and this year is no exception. What's interesting about this year's Twisted Christmas Event is that's there's some neat crossover with the first-person puzzler The Ball.
First up, there's two new maps and achievements along with the return of all the Christmas-themed mutants from previous years. You'll also get a chance to get the Zed Gun and Baddest Santa again, if you didn't manage to get the unlocks from a previous event.
If you already own The Ball, you'll unlock Harchier Spebbington (which is the best not-really-an-upper-class English name ever) as a character skin which was previously only available as a pre-order. There's also a new two-hour mini campaign for The Ball and all of this is free if you own both games. If not, both are reduced to half price right now and Killing Floor is free to play until January 2. Killing Floor might be looking a bit old now but you can't argue with a game that's been supported this well with free and paid DLC.