The Badlands
Overgrown with anomalous strains of hive like entities, the badlands are impossible to inhabit due to the lack of livable areas or space to distribute farm modules. Not to mention the infected horde which wander, collecting any and all consumable organic or otherwise material back to the hives for absorption or conversion to more infected/drones. The air is filled with spore like gasses which make breathing difficult and causes sickness after exposure. While there are methods to heal and cure people from the spore lung infections, anyone who stays in the badlands too long is liable to succumb to the spores and slowly turn infected in a long and agonizing process.
The Fringe
Icey and unforgivingly cold, while the Fringe can be inhabited, it is impossible to do so outside of protected and constantly maintained modules. While the majority of planet Earth is cold, the Fringe is the worst of it, temperatures usually at their height only just above freezing, otherwise sinking to ruthless tundra. The Fringe is known for having the most unusual and difficult anomalies to study, detect, or deal with. Gravitational, thermo-anomalies, and several other ghost like, untraceable anomalous traits. To travel into the Fringe without anomaly ready equipment is a death sentence. A great deal of the Fringe is vast, flat land, sometimes with occasional cold resilient plant life near the edges or pockets of the warmest areas.
The Bogfields
As the name suggests, the bogs are reaches of land where water dominates and makes travel nearly impossible save for the use of airboats and upwardly propelled craft. Aircraft is basically no good in these areas due to the constant density and high reaches of the fog and clouds. The air isn't unpleasant to breath necessarily in most places, but it is heavy and rich in water molecules. The atmosphere provides no benefit nor grand reduction to the infected, but it does deter them from making hives in these lands as the fungal spores travel with greater difficulty through the highly humid atmosphere, falling to the ground by the slow and steady mist fall.
What were once countries, would serve the interplanetary terran collective as factions and vassal states, each former nations leadership a part of a larger council of unified central governing system of planets. History of the countries and how or why they finally found peace and merged has since been lost entirely to time. Even the names and borders of most individual countries is not easily remembered.
Travel was hastened by advancements in spatial warping technology and drives, the promise of greater distances being traveled within months or weeks rather than many years across multiple generations was becoming more of a reality as discoveries of Slipfold - Interstellar Travel engines were transitioning from theory to experimentation with promising results!
It was then the advancements of AI crossed its previously known boundaries. Nomadic dwellers and tribes of robotic people were discovered among asteroid fields and pockets beneath moon and planetary surfaces. The origin of these beings was unknown, but the excitement of their discovery did not last.
4547 AD:
The first settlement of Pluto was celebrating its completion when the Kah'Rul came. Strategically timed when all defenses were down, the governing and military officials majorly in one place. With the hubris of human growth leading failure of outer space possessing life, the massacre took eight years to reduce humanity to its final stand on Earth.
The war began briefly on Pluto. Critical figureheads now dead in the initial Pluto massacre left other, less experienced officers to take charge, mostly scattered and unprepared across the solar system. Planets and moons, one by one the colonies fell. Shuttles fled back to Earth in evacuations and strategic retreats to bolster the defenses on Earth, but the Kah'Rul were ruthless and far more prepared for their invasion process.
4655 AD:
Culture was destroyed, history was wiped, the Kah'Rul enslaved all they captured while the rest fled underground to form resistance villages as far from the invaders as possible. Over time, many Dasarin had joined the human resistance, seeing opportunity to break from their enslavers. The planet was riddled in desolation with a formerly prosperous society turned into a war torn scarred barely surviving society. Walls and sectioned cities, some visible from space where the last cities stood.
4660 AD:
The Kah'Rul had already begun capturing human survivors and indoctrinating them into their "Peace Keeper" corps, however. Among these was John Weller, brother of Jack Weller, the founder of the Specter Initiative. Fifteen years after the invasion was complete, John and Jack were reunited and John freed of his mental conditioning. Reclaiming their previous lives as both mechanical and software engineers, John and Jack worked together to begin teaching the resistances how to reverse engineer what ever Kah'Rul technology they could get their hands on, vastly turning the tide of the war.
4677 AD:
Seventeen years later of careful planning and construction, enough armaments and bases were created to mount a proper offense against the Kah'Rul. The primary targets were Shipnets which the Kah'Rul required for interstellar travel between worlds. Taking out these targets would strand all local Kah'Rul loyalists and colonies, disallowing for any reinforcements or connection to their other worlds. The arrogance of the Kah'Rul allowed them to fall under the assumption that such a thing would never be possible, bringing them to leave Earth and its system relatively unprepared. There were however, consequences to the destruction of so many Shipnets all active and all at once. A ripple formed, cracking the barriers between dimensions and spacetime. Other-worldly creatures and anomalies began to flood into Earth with reckless abandon, even a few unlucky souls being captured in the wake and turning into anomalies themselves. This ripple would be felt across the Galaxy.
The year is now 4681:
The Specter Initiative holds strong, uniting many of the resistances into one new governing body known as the Federation, the Specter Initiative remains the military branch. With the combined effort between the humans and other previously enslaved races by the Dasarin, Earth has begun to see the lack of Kah'Rul enforcement holding up in their smaller outposts, terraforming machines the Kah'Rul were using to cool and darken the planet are being destroyed one by one as their grasp begins to fail. Towns and cities have begun to sprout up in safe areas, walls of the war from the fall of Earth reutilized to provide expansion, new technology re-emerging to learn about the new anomalous presences, and weapons from a bygone age when the planet had its own little wars uncovered and recreated, adapting to their new duty to protect Earth.