"Ultima Ratio Regum" (The Final Argument of Kings) - an Ancient Earth Latin inscription found on each XM-5 unit, usually on the torso or forearm
The XM-5 Hercules is a gigantic, 80-meter-tall bipedal humanoid robot fielded by the Directorate. Developed as a means of combating the Mortis's largest constructs without resorting to high-yield nuclear weapons or orbital bombardment, which destroys entire swathes of ground and has a high friendly-fire potential, the XM-5 machines are the ultimate in conventional warfare systems.
A Hercules is a giant human-piloted automaton standing 80 meters tall [or about as tall as the Statue of Liberty from the base to the torch in her upraised right arm]. Each machine weighs about 10,000 tonnes and mounts an array of weapons onto a broad-shouldered, humanoid chassis. They are piloted by crews of six men, lead by the "Dux Corporis", who usually holds the rank of Colonel [as each individual mech is treated like an entire Brigade].
The Hercules's primary ranged offensive weapon is the large modular missile banks on its shoulders, which are designed to mount a number of standardized modules of a fixed size. Thus, the capacity of each module varies by what kind of missile it is fitted with - usually a mech will carry mixed batteries of 152mm anti-air/anti-armor missiles and the more destructive 300mm missiles, intended for use against hardened ground targets or large, high altitude exoatmospheric craft such as gunships and even corvettes. For dishing out fire against lighter targets, the huge Automaton also has two paired 300mm Magnetohydrodynamic cannons on each wrist, a total of four twin-linked dual barrel modules. These are essentially dual versions of the main gun of a Carnifex tank, but with twice the bore diameter, a perportionally longer barrel and a much higher rate of fire, functioning as gigantic autocannons. Using these weapons, a Hercules may lay waste to entire swathes of enemy armor or hardened positions and even do damage to the largest of Mortis creatures from a medium-to-short range distance. For self-defense, the mech is equipped with a huge array of Energy Screen Projectors with several layers of redundancy, multiple overlapping electronic warfare suites spaced throughout its body (each controlled by its own AI) and a system of hundreds of automated point-defense lasers which are also more than capable of damaging enemy aircraft and light armor at short ranges.
Having said all that, however, the Hercules is an extremely advanced and controversial piece of equipment. It requires the attention of a highly advanced artificial intelligence simply to move and balance itself, while the massive artificial carbon nanotube bundle muscles - stimulated by an array of hundreds of electric motors of various strengths - are extremely expensive and time consuming to create. They must be "grown" using costly nano-construction processes to ensure a seamless and perfectly regular, balanced arrangement, due to the scale of the massive machine - even the slightest irregularities could cause major structural problems. The towering Automaton's skeleton, made from an almost-indestructible carbon composite, is equally expensive, as it requires the same gravimetric compression process as used on Directorate vehicle and infantry armor - albiet on a truly megalithic scale. Finally comes the robot's "skin" of layered ceramic-composite and tungsten plating (again, basically scaled up from what is found on any other Directorate vehicle), which is an extremely intricate network of overlapping and interlocking plates that flex and shift to accomodate the massive amounts of gravitational force and raw torque generated by even the simplest of limb movements.
Although the Hercules mech bristles with weaponry, its primary means of engaging the Mortis's gigantic "super constructs" - the beasts it was designed to fight - is the huge robot's own body. Using a system of powerful ion thrusters, the mech is capable of great unnatural bursts of speed it would not otherwise be able to achieve, and it literally grapples with the monsters and beats them to death. These Constructs are truly massive creatures encased in armored shells with many powerful, taloned limbs. They are, however, quite slow - intended to function as hulking biological battering rams rather than to fight against anything as enormous as themselves. Gravity works against them, as their bodies lack the awesome power of a Hercules's artificial muscles. In one-on-one combat, the mechs have a decided advantage: they can cripple the alien titans from afar with their missiles before closing in for the kill if necessary, or simply crush them in hand-to-hand combat.
The greatest threat to a Hercules is generally enemy air power, and they are never deployed until the hostile air force has been crippled. Against the Mortis, however, the mechs can be brought into battle almost immediately, since the aliens lack anything resembling a proper fighter jet: the flying Constructs are slow and extremely vulnerable to the robot's missiles.