The real reason behind the apocalypse...the real reason for Crow's offensive...the secret behind the creation of the XMs...all of these would be revealed at the pivotal moment, as the crew of the Arbalest raced towards their final battle. For it was there, as the light of triumph neared their grasp, that the true depth of the threat facing humanity was revealed. With the army of XMs devastated, the crew advanced upon Crow's headquarters, mere moments before a monster the likes of which they had never seen broke free from its depths. The Nimzo, the Grandmaster, the mother of all XMs. It was devastatingly powerful, nothing like anything the crew had seen before. All the firepower at their command was needed to bring the monstrosity down, at which point it was revealed that Damon Crow was already dead of a failed heart, and had been for three days.
The Nimzo towered over every other unit of its time, be it AT or XM, at a whopping fifty meters tall. It tended to slouch due to its own weight, the bulk of which was concentrated in its massive three-clawed hands. The beast's body structure was only mostly humanoid, while its internal biology was like nothing on this earth.
Possessed of enormous strength and power, the Nimzo had only average reach, but could devastate in close combat - its claws had power enough to crush the Kerykeion Mark III's thruster pack as though it were made of paper. It could also close its fists to generate a powerful barrier from the glowing spheres embedded in its palms and chest. Perhaps even more dangerously, it could spawn larvae on its own - without their armor, the younglings were nearly as dangerous as Ladjas. However, these spheres were also its weak point - a combined shot from the Kerykeion Mark III and Pheora managed to puncture its barrier and strike the orb on its chest, causing it to overload and explode violently.
In the aftermath, Ian Corusa would inspect Damon's office personally, and would there find his body along with information that changed everything. Nearly 70 years ago, Damon had come in contact with an alien being who went by the name of Syn. As a token of goodwill, she granted him Nimzo, which she used to spy on him and through him humankind for decades until he found a means of controlling it and its spawn through spinal entry plugs and restrictive armor. The war had only been the beginning - the XMs were created as a vaccine to prepare humanity by forcing it to develop the Baryonic Drive, the power that could stand against Syn's kind, and the vessel to use it. It was all for the survival of humankind. And so, as the sun set on Crow's hollow empire, the true threat began to stir...
During the second half of the war, multiple Nimzos would be faced by humankind, often in the company of lesser alien varieties.