Watch out for Witches and Boomers, because Francis, Bill, Zoey, Louis, Coach, Ellis, Nick and Rochelle from Left 4 Dead 1-2 are coming to Zombie Army Trilogy.

Valve and Rebellion have announced that the cast from the undead first-person shooter co-op series, Left 4 Dead, is heading to Zombie Army Trilogy for free. Starting today, the walker-slaying survivors of L4D 1-2 are heading to 1945 as the newest playable characters added to Zombie Army Trilogy, which now doubles the game's roster to 16 different characters. Whether you want a reunion of the old team or want to partner up Bill Overbeck and Karl Fairbune, you're able to take on the Third Reich's rotting army with some fresh faces.

In order to explain why the modern day heroes are able to travel back to 1945 and take on zombies, 2000 AD released a free comic that you can download. Best of all, Steam has slashed Zombie Army Trilogy's price by 66 percent. The sale will last from Aug. 20 until Aug. 24. This means that game has been discounted from its usual $44.99 price tag to a mere $15.29.

"We're delighted to be able to bring such iconic characters to Zombie Army Trilogy," said Rebellion CEO Jason Kingsley. "As thrilling zombie shooters designed to be enjoyed with friends, Zombie Army Trilogy and Left 4 Dead share a lot of common ground. Our offices are filled with people who enjoy Left 4 Dead during breaks, and at lunchtime you'll usually hear a few yells of 'Boomer!'

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