Team Fortress 2's annual Halloween celebration is here, bringing with it a host of new content, achievements and zombies! It begins now, right now, go play!

An addition to the Mann vs. Machine mode leads the pack, with a new mission called 'Wave 666', giving your team of six a zombie horde to contend with. Did I mention the horde is 800 strong?! As well as this, a new King of the Hill map is present, featuring a magician called Merasmus who serves as the boss. There also are news achievements, as well as the interesting inclusion of spells which players can cast on their items. Read more from Valve on the update here. As ever with Halloween (and full moons) all your Halloween themed items are now visible!