There are many theories and mysteries surrounding the origin of the Combine, yet none have been conclusively solved. However, with the assistance of the Salvatians, we may uncover more about the Combine, though much remains speculative regarding the Universal Union—better known as the Combine.

To understand them, the Combine, also referred to as the Universal Union, is a vast, multidimensional empire that functions as an oppressive, highly advanced, and dystopian force. It seeks to conquer, exploit, and assimilate entire species, planets, and dimensions for its own expansion and survival. Their true nature remains entirely unknown, even to those within omniversal realms, making their very existence a mystery. However, what is known is that they originate from a world called Overworld—a planet highly inhospitable to humans or any sapient beings, as its environment is unsuitable for respiration.

From what we have gathered, the governance structure of the Combine is ruled by a humanoid being who calls himself the Combine Overlord. Unlike the rest of the Combine's race, he bears a resemblance to a human in appearance. However, his true identity remains unknown, as he always wears a helmet that conceals his face, preventing us from determining his exact species.

As the supreme ruler of the Combine Empire, he holds absolute dominance over other species, which the Combine considers inferior. Beneath him are his loyal subordinates known as Advisors—large, pale, super-intelligent, grub-like creatures with no discernible facial features. They have a device resembling a gas mask attached to their front end or "snout," suggesting that they require a breathing apparatus to survive on Earth or other non-breathable planets.

Lacking visible eyes, they rely on a cybernetic eyepiece on the left side of their faceplate for vision. Their bodies are encased in a skin-tight, olive-green bodysuit that covers everything except their extremities. A collar adorned with strange golden glyphs encircles their "necks." Additionally, a pair of thin, black robotic arms is implanted into their backs, enabling them to lift an adult human with ease and even support their own weight.

They also possess an appendage resembling an elongated tongue, similar to an invertebrate's proboscis, which can extend from their mouths. Most notably, they exhibit extraordinary psychic and telekinetic abilities, though the origin of these powers remains unknown. It is possible that their abilities stem from their existence in a dark realm.

The goal of the Combine Empire is to dominate and assimilate every world across multiple dimensions. This extends to the multiverse, effectively making them a multiversal warlord. When the Combine conquer a species, they subject them to both biological and mechanical alterations, stripping away their individuality and turning them into brainwashed, enslaved entities that serve the greater whole. This process ensures absolute loyalty while eliminating any possibility of rebellion. Their conquest of worlds follows a systematic approach: dismantling native ecosystems, suppressing local technology, and repurposing biological entities to fuel their war machine.

Their military force is primarily composed of Synths—biomechanical beings that are cloned and synthetically engineered by the Combine. These modified organic-mechanical entities are equipped with advanced weaponry and possess exceptional durability. Additionally, the Combine forcibly transform conquered species into enslaved synthetic beings, such as Vortigaunts or Houndeyes, altering them into cybernetic warriors capable of unleashing devastating attacks. Synths commonly exhibit organic features such as compound eyes, segmented legs, and skin-like textures, heavily contrasted by mechanical components implanted into their bodies, including weapons, propellers, and propulsion engines.

Another major military division is Overwatch, an organization composed of Transhumans—former humans who have been surgically augmented, reengineered, and brainwashed into unquestioningly loyal soldiers. These transhuman soldiers possess enhanced strength, speed, and durability due to their extensive modifications. Overwatch, as a transhuman military force, was established when the Combine discovered a human-inhabited planet called Earth. Their invasion led to the infamous Seven Hour War, which resulted in the swift conquest of the planet and the subjugation of what remained of humanity.

They possess a formidable navy with numerous space warships capable of conquering stars and planets through domination and annihilation. These warships are used to seize control of planets through various means, including orbital bombardments and the elimination of enemy vessels that stand in their way.

The Combine wield an incredibly powerful technology known as Dark Energy. While its origin remains unknown, it enables them to develop technology far beyond conventional advancements. One such creation is the Suppression Field—an ominous device that prevents humans and alien species from reproducing, allowing the Combine to maintain strict control over their enslaved populations. Another is the Dyson Sphere, a structure designed by the Combine to harvest vast amounts of energy from a star to fuel their war machines.

Speaking of war machines, the Combine have developed a vast array of vehicles, aircraft, and spacecraft, often incorporating designs from subjugated species into their military arsenal. The Fabricators exemplify their technological prowess, serving as advanced systems capable of upgrading weapons through fabrication—though they require resin, a raw material essential for weapon modifications.

Another fearsome innovation is the Confiscation Field, a device capable of seizing and destroying unregistered weapons. This technology effectively disarms enemies, rendering them defenseless, while ensuring that only Combine forces can safely wield their weapons, as they are registered within the system.

Furthermore, the Combine have harnessed Dark Energy to manipulate dimensional portals, granting them access to alternate universes, which they seek to conquer and assimilate, erasing all resistance in their path.

Another terrifying piece of Combine technology is the Planetary Interceptor, a colossal planetary-class vessel and the largest warship in the Combine Navy. It is capable of harvesting a planet's molten core for resources and is equipped with a powerful energy cannon capable of destroying entire sections of a planet. The Interceptor is approximately the size of Earth.

For interstellar travel, it utilizes wormhole technology, a topological phenomenon that creates shortcuts between two points in space-time. This allows the Interceptor to link two locations separated by immense distances, such as many light-years apart. In essence, a wormhole functions as a tunnel, with entrances positioned at different points in space.

The Combine eventually developed a new technology known as the Clone Machine, which enables the mass production of both Transhuman soldiers and synthetic beings. This ensures they never face shortages of manpower, supplies, or weaponry, securing their military dominance.

With these advancements, the Combine expanded into even more dimensions, seeking to conquer and assimilate new worlds. Their mastery of multiversal travel granted them the ability to extend their reach across countless realities, continuing their relentless campaign of conquest.

To make matters worse, reports indicate that the Combine have developed a new form of technology capable of concealing or even eliminating deities that pose a threat to their rule. Shockingly, their advancements in Dark Energy may allow them to defeat gods, disrupting the balance of power in the multiverse. This development has caused significant distress among divine entities, as even they find themselves unable to stop the Combine alone.

For a time, their conquest of different dimensions and universes proceeded unchecked—until a new enemy emerged, threatening to derail their ambitions and altering the course of history for the first time.

On that day, the expeditionary space fleet from the Sovereignty Republic of Salvatia—ruled by Supreme Sovereign Xavier Salvador—arrived to rescue the remnants of humanity in the aftermath of the Citadel's destruction and the death of the Combine's puppet leader, Dr. Wallace Breen. As a result, they successfully prevented the death of Eli Vance.

After the Salvatians, alongside their human and Vortigaunt allies, fought back against the Combine forces on Earth and sealed the portal to Overworld, they began terraforming the planet using the Genesis Ring—a colossal, planet-sized, ring-like ship. In the meantime, the resistance established a provisional government. The Salvatians also deployed military instructors to train resistance fighters, transforming them into a well-organized and functional military force through rigorous training.

Both the Grand Army of Salvatia (G.A.S.) and the Vindictarium Order were dispatched to contaminated lands infested with Race X and hostile Xen species. They also ventured into uncharted wastelands in search of human survivors while eliminating Combine remnants and hostile human factions, such as marauders and raiders. Once Earth was secured, Salvatia turned its attention to the Combine's conquests across different dimensions and universes.

The Combine is regarded as the most significant threat to the multiverse, as they relentlessly pursue their goal of conquering and assimilating all sapient life. Recognizing that the Combine Empire is beyond negotiation, the Sovereignty Republic of Salvatia formally declared war on them—along with other multiversal warlords who possess multiversal travel technology or magic artifacts. The Combine has since become Salvatia's primary adversary.

For now, this concludes our current knowledge of the Combine Empire. However, we will continue gathering and analyzing information to further speculate on the true nature of their dominion.