The Combine is the primary antagonistic force in the Half-Life universe, first appearing in Half-Life 2. They are a vast interdimensional empire composed of multiple species and technologies assimilated from countless conquered worlds in the multiverse. Ruthless and technologically advanced, the Combine would come to dominate Earth following the events of the Seven Hour War, reducing humanity to a subjugated species. The true size of the Combine is unknown, but is nonetheless implied to be on a cosmic scale. Similarly, the Combine's origins and overall goals are shrouded in mystery, but it can be assumed that their ultimate ambition is to endlessly conquer and assimilate all throughout it holdings. Details of the Combine's true leadership and administrative structure are unclear and remains mysterious even by the time of [[, but Alien beings called Advisors, ensconced within the Citadel, assume responsibility for overseeing Earth's slow 'integration' into the Combine, 'advising' through Dr. Wallace Breen, the chief human collaborator who serves as the appointed 'Administrator' of Earth. How long the Combine has existed is also unknown, however the All-Knowing Vortigaunt stated that the Vortigaunts were enslaved for eons: ("We have endured these chafing bonds for eons, yet a single moment of further servitude seems intolerable!"). That could mean multiple billions of years. However, this could also be in reference to the Nihilanth. Almost all known information about the Combine is gathered from their conquest and cruel rule of Earth, which signifies a highly militaristic and totalitarian 'culture', if such a term even applies. The Combine forcibly assimilate the dominant species from the worlds they conquer (which, in Earth's case, is humanity) and then manipulate these species through bioengineering and invasive surgery, twisting them to fit the Combine's pursuit of cruel perfection. The results of the Combine's re-engineering processes are "synths" — synthetic organisms augmented with Combine technology that serve a variety of functions within the empire, from weapons of war to mindless slave drones. A Combine Advisor. A Combine Advisor. Vocal stress is on the first syllable. The name is pronounced COM-bine, as in Combine harvester, opposed to the verb form com-BINE, as in "to join together or unite." Dr. Breen refers to the Combine Soldiers and Civil Protection as "The Transhuman Arm of the Combine Overwatch" in Nova Prospekt, implying that "The Combine" is an accepted name of the empire, at least among the Earth-based Overwatch. It has since been revealed that the Combine originally invaded the homeworld of the Nihilanth's species and inflicted a campaign of genocide against them, with only the Nihilanth able to escape the slaughter by seeking refuge in Xen. It brought with it members of several species, both its allies and its slaves, including the Vortigaunts. Following the Black Mesa Incident and subsequent Seven Hour War, Earth then became the Combine's most recently known annexation. Earth's dominant species were modified to form a new arm of the Combine military, and the planet's resources were systematically stripped away. Mighty as they are, the Combine are not without weakness. Despite their enormous size, or perhaps because of it, they are "slow to wake" and mobilizing their vast power requires great effort and time. Their limited and slow teleportation technology, whilst still impressive in its own right, is a field in which even the Resistance is more advanced, as they are unable to translocate in local space the way that the Rebels can with their superior methodology. As such, they are vulnerable to clandestine guerrilla warfare tactics, and ultimately suffered a string of defeats resulting in a general collapse of their control on Earth following The Uprising.