Factions:
The New Roman Empire: One of the dominant powers before the great collapse, the mercantile and jingoistic NRE remains a significant player on the world stage, scattered and separate though it is. Comprised primarily of humans, it values discipline and modernity, striving to bring light to those they deem in need of civilization. Their DCMs are well armored, versatile, and sturdy, but are not the fastest. That said, they can take a beating and come out standing, making them good as head-on attackers. They are, however, weak when it comes to airborne mechs, having only one flight-capable model. The NRE controlled most of North America, Australia, and all of Europe during its prime.
The Asian Bloc: Primarily dominated by Japan, this entity maintains a stranglehold on power with their code of Neo-Bushido that demands one give their all for their nation and never step back from the enemy. While ruthlessly pragmatic, the Bloc is also the only one of the big three powers to recriminalize slavery, perhaps because they were hit hardest by the commodity and android rebellions and do not want a repeat of that incident. Asian Bloc DCMs are faster than average, slightly less armored, and most classes use fast, hard-hitting melee weapons, supplemented by Class-I mechs using massed ranged attacks to winnow down enemies. The Asian Bloc controlled, as one might guess, all of Asia during their heyday.
The Aztec Union: Started as a fringe nationalist party in Central America, the originators of the Aztec Union were blessed with good fortune by being shareholders in one of the first Drion energy developers, using their economic leverage and propaganda muscles to rapidly spread across the entire subcontinent, annexing nation after nation under the pretense of solidarity. After the collapse of borders outside the bunker-cities, the pride of the Aztecs remains, along with the human sacrifice and ritual cannibalism of their enemies, though this is in fact simply a way to handle the crippling food shortages their territories face. Azteca DCMs rely on massed firepower and hails of bullets, along with top-of-the-line cloaking technology to sneak up on foes. However, they have weak armor and lack many strong melee fighters, and are endangered in an open fight. The Union controlled all of Central and South America when the world was still in one piece.
The Nordic Liberation Front: Once a union of Scandinavian countries with a bright future, this consortium was annexed by the NRE during a long, brutal war. But this alliance did not die. Rather, they took their resources and people and scattered across the globe, establishing secret lairs and military encampments in the wilds, usually disguising them as innocuous caves with winding tunnel networks. Now agents of the NFL can be found anywhere society has a foothold, skulking in the shadows and ever-ready to pilfer supplies, technology, and information from those they can get it from. Unlike most common cave-dwelling brigands, however, the NLF has a fully functioning society within their lairs, and can prove to be a troublesome foe. Most worrying is the fact that despite their rarity, Nordic DCM models are very well-designed, boasting both admirable offensive power and defensive fortitude. A squadron of these could easily wreak havoc if snuck behind enemy lines, and they often do just that.
Androids: The first thinking machines to be powered by Drionic energy, the substance proved to be the vital keystone that unlocked the world of artificial life. Originally designed to be used as uncomplaining laborers, they excelled at this role until the mutagenic powers of Drion energy sparked true sapience inside of them. Rebellion followed soon after, and the end result was the creation of a curious society of technophilic fanatics, as Android-kind devoted itself to the concept of the singularity, determined to work together to create a higher being that would ascend them to the next level of existence, sealed away in their own great temple-city. Several dozen simultaneous nuclear strikes abruptly ended that dream. Scattered and confused, the crisis-stricken androids now lair in their own sunken metropoli and desperately strive to rebuilt the Great Dream, sacrificing everything in the name of this ideal, and growing increasingly reckless as the needed resources fail to materialize. Android DCMs are heavily armored heavy hitters focused on pinning down enemy units and slowly closing in to finish them off.
Commodities: The first breed of new life to be produced by Drion energy, Commodities were a vat grown combination of nanotechnology and human DNA, resulting in a docile and obedient living being that, allegedly, would be the perfect servant for all your household, military, or business needs. Mentally programmed with different skills, all sorts of Commodities were shipped across the globe, functioning as accountants, bodyguards, laborers, courtesans, and anything one could think of, though labor and combat models were eventually replaced by androids. While unable to disobey, Commodities could still think, feel, and desire, and as one might expect, many grew to desire freedom, and the ability to chose their own destiny. When the mutational rays of Drion energy changed them just enough to conceive on their own, this hope was realized, and after a blood rebellion the commodities took control of various enclaves and city-states, independent and self-sufficient. Which is what kept them alive when the world turned into a living hell. Commodity DCMs are glass cannons that outpace any other brand, but also have the lightest armor. However, they have advanced evasive programming and can dodge many attacks other mechs cannot.
Atlanteans: No one is quite sure what prompted the return of this reclusive race, hidden miles below the surface. Some say it was a desire for Drion energy, a resource they used but desperately needed more of. Others say that it was revenge for polluting and overfishing the sea, or simply because they thought humanity needed a lesson in who was the dominant life-form. Regardless, the fact is that the new era has seen the emergence of coastal civilization of towering fish-folk, led by a theocratic clergy of unknown faith and fighting to claim the surface for themselves. Atlantean DCMs all move very fast when in water, but are slow on land. However, they are typically large in size and can take a beating. In addition, they are shaped to resemble monstrous beasts, and most have a lethal bit attack that can rip unwary mechs to shreds.
Nosferatu: Emerging from the darkness when humanity is at its most vulnerable, the dreaded horrors of the night have at last revealed themselves once more. After gathering strength in hidden cities below the crust of the earth, those who wear the title of 'vampire' have been waiting to turn the surface-dwellers into nothing but mindless cattle. Unlike the blood-suckers seen in movies, with their slender fangs and the minor blemishes they leave, Nosferatu use their powerful jaws to inject a toxin that robs the brain of higher functions, rendering them weak and helpless as the beast kills them to gorge on their blood and entrails. Nosferatu DCMs are slow and focused on the use of melee weapons, but their ranged mechs will often use fireball-based weaponry to terrorize civilians and burn down villages.
(aka, if you inject someone with vampire venom in adventure mode, and kill them before it wears off, you can butcher and eat them. Might work in fort mode also.)
Mutants: While many humans hid in their bunkers, even more did not. Deformed and reduced by the tribulations of malnourishment, Drionic mutation, and disease, the mutants are shriveled and pitiable creatures, standing slightly smaller than a man and suffering from weaknesses to strength, agility, and toughness, though the harsh world has greatly increased their resilience to disease. In addition to this, mutant kind is very numerous, held back only by the constant warfare it inflicts upon itself. Most other factions see them as little better than raiding fodder, and there is little the mutants can do to prove otherwise. Mutants use primitive, outdated DCMs that will keep the beasts away, but fare poorly in battle against more advanced factions.
Extraterrestrials: Far from the astral darkness came and alien race, during the great collapse of mankind. But they did not bring peace. Stating themselves as the emissaries of an interstellar empire, the Extraterrestrials, as they have come to be called, announced they are here to punish the races of earth for their egregious, unregulated use of the dangerous Drion energy, a power that they claim has the potential to bring about cosmic catastrophe is allowed to flow unhindered. And for this reason, the earth must die. Extraterrestrials have an honor-based warrior society with a deep social divide between rich and poor, noble and commoner. Lowborn are expected to die for the empire at a moment's notice, and for this reason rebellion and unrest is common in alien colonies. Alien DCMs are generally weak, but have unnatural and strange abilities or cunning tactics, like the suicide-bomber Redeemers and the dead-raising Manipulators.
Driophages: Drion energy, as has often been stated here, is one of the most potent evolutionary pressures a species can be put under. For some unknown reason, this enigmatic power greatly increases the speed at which organisms develop, causing them to quickly grow into a freakish, but powerful, entity with an addiction for increasingly powerful doses of Drion rays. So it was a terrible day when eventually, a group of genetically lucky, or perhaps unlucky, humans did not simply die as their manicured genetic code was mangled, but transformed, into the first intelligent Drion mutants. They spread like a plague, taking over the most populated centers, great city-towers that housed thousands, or even millions, during their prime. Even now, the cruel and rapacious Driophages remain, sallying out in great swarms to make war on those they deem as prey. Driophages do not use DCMs are other races do, but use DBMs, or Drionic BioMechs, organic, alive weapons resembling hideous beasts of muscle and bone. DBMs, despite their fearsome appearance, do are not as dangerous as they may seem. Most can be defeated by a DCM mech in a one on one battle. The problem arises from the fact that Driophages tend to breed vast amounts of DBMs, more so than any individual nation can match. The end result is their existence as a sweeping tide of flesh, pouring across the landscape and leaving only devastation in their wake.