Team Fortress 2 comic, robot heads and massive tank tease new faction and MvM mode

Something big is afoot in TF2 land. A post on the Team Fortress blog confirmed that, on Saturday night Valve “launched our most fiendishly difficult ARG yet,” an ARG they declared to be “diabolically, even needlessly complex.” The TF2 community swiftly solved the conundrum revealing a comic unveiling a third Mann brother Gray Mann. Cold, calculating, fiendishly smart and quite evil. Essentially, he’s Team Fortress 2′s G-Man.
But what’s this mysterious stranger plotting? The evidence at the moment points towards “evil robot army.”
Folks on NeoGaf and ValveARG have been picking out clues from the Team Fortress 2 updates of the past year or so, and have discovered, via secret rooms in Foundry and Doomsday maps, regular coded references to “Gray,” who we have now been introduced to, and “MvM,” which is thought could refer to an incoming Man vs. Machine mode that could see Red and Blue factions uniting to fend off the metallic menace.
Community members have picked out blurry background photos and bits of background art that seem to hint at humanoid robot designs, fuelling speculation that a third, robotic, AI controlled faction may be on the way. The robotic army part of that theory is supported by the discovery of these robotic head model tucked away inside the Source Filmmaker files. They look like this.

Then there’s the tank that’s started appearing in map skyboxes. It’s big. Big enough to carry an elephant. Or a ROBOT ARMY.

The whole saga is helpfully summed up by the video below on Kotaku. A Kotaku reader also explained how the ARG went down:
“Someone found out by equipping an item that was not supposed to be equippable and high fiving someone, the person you high fived would receive a secret message in the form of a joke. The jokes turned out to be hidden hex code, which then revealed nine things. Eight of them just revealed a word, but the nineth one revealed a zip with a password lock (a Keepass thing). Using the words as a PDP code list somethignsomthingsomething(I’m not exactly sure here), people found a link inside linking to tf2.com which turned out to be a crafting recipe in game. Crafting all the items together caused a GAME wide message, linking the comic.”
The clues have been building for months, but the release of the comic suggests that the Man vs. Machine update is imminent, which is exciting. And genuinely a bit menacing. Allow the music in the MvM evidence video to strike to strike the necessary conspiratorial tone.