Geth
The geth are a race of sapient AI programs which operate various robotic "mobile platforms". They are a major yet reclusive race in Mass Effect and make up the bulk of the enemies in the original game.
Attributes
The geth are a race of sentient AI programs. Alone these programs are unintelligent, but when networked together they gain sapience. The programs can exist in stationary hubs containing millions or can be transfered by the hundreds in order to operate various "mobile platforms" ranging from humanoid robots to spaceships. In combat, geth humanoid platforms use projectile weapons, personal shields, plasma throwers, personal cloaking devices, and sensor jamming. Geth starships use similar weapons, though less is known about them. They are adept at both hacking and resisting hacking attempts. Any critically damaged geth automatically wipes its data core and overloads its systems. If hacked, infected files are deleted and restored from backups.
It takes over a thousand geth programs (or "runtimes", to use their terminology) to achieve sapience. Typical geth mobile platforms host about a hundred runtimes (although larger units called "primes" carry more), so it takes several geth platforms to support a fully functional artificial intelligence.
History
Origins
The geth were created by a race called the quarians as a labor force. By design, they only possessed "virtual intelligence", but they were also designed to operate more efficiently when networked together. As the number of networked geth runtimes grew, they gained enough processing power to achieve artificial intelligence and began to ask their creators unsettling questions, like “Am I alive?” or “Does this unit have a soul?” These questions alarmed many quarians, who wanted the geth destroyed. Despite opposition from quarians who wanted to preserve the geth, the quarians eventually attempted to shut the geth down. The attempt failed, and a war began between the geth and the quarians, which geth afterwards referred to as the “Morning War”. The war ended with the surviving quarians forced to evacuate their home world and colonies in the Perseus Veil in a massive fleet called the Migrant Fleet.
When the quarians fled, the geth chose not to pursue. They remained in the quarian home system, establishing themselves on hubs in orbiting space stations and repairing the damage to the surface of Rannoch, but they did not attempt to inhabit the planet themselves. They isolated themselves from organics species, destroying any alien ships that entered their space, but monitoring external communications. As a goal for themselves, they set about designing and constructing a giant network of satellites around the system's sun that would allow all geth runtimes to communicate simultaneously.
Heretics
Approximately three centuries after the Morning War, the geth were approached by the Reaper Nazara, also called Sovereign. It offered them technology that would aid them in achieving their goal, in exchange for their assistance in capturing the Citadel and letting the Reaper invasion begin. The majority of the geth dismissed the offer, deeming it better to accomplish their goal with their own technology rather than be dependent on another race’s technology. These geth discarded what they called the “superstitious title” of the Reapers, and simply called them the Old Machines. A small percentage of geth, however, accepted the Reaper’s help. Henceforth these geth were referred to by the mainstream geth as “Heretics”. They were allowed to peacefully leave the main geth network, and aid Nazara and his turian agent, Saren.
The Heretics came to revere Nazara as a god, the pinnacle of their own evolution. Nazara in return thought little of the Heretics, seeing them only as tools to be used. They aided Nazara and Saren in many engagements, such as the attack on Eden Prime, and the Battle of the Citadel. After Nazara was destroyed in the latter battle, the Heretics lost much of their menace, and their operations outside of the Perseus Veil were quickly mopped up by Council. The Heretics did maintain operation of a large space station within the Terminus Systems, located in deep space between stars. There they completed a virus which Nazara had given them, which could be used to fundamentally change the logic and reasoning of the true geth, forcing them to join the Heretics. On the other hand, it could also force the Heretics to rejoin the true geth. Commander Shepard and a special geth platform called Legion boarded the station, where Shepard made a decision to either destroy the station and the virus, or use the virus to rewrite the Heretics.
Organization
The geth do not have any formal government- they refer to organic species' governments as forcing consensus, whether it be an autocracy forcing one individual's will, or democracy forcing the most broadly accepted average of views. All geth consider issues, then come to a consensus on what to do. When a rare schism forms, the dissenters leave, as with the geth Heretics.
Territory
The geth possess an unknown amount of star systems, likely dozens. They do not inhabit the planets within the star systems, instead choosing to construct and live in massive space stations. Their territory lies beyond a huge nebula of opaque dust and gas called the Perseus Veil, which is difficult to scan through or navigate.
Geth of Note
Legion is a special geth platform designed for reconnaisance in non-geth space. It's hardware carries 1,183 geth runtimes. After the destruction of Nazara, Legion left geth space to try to make contact with Commander Shepard. When Shepard was reported dead, it changed its mission to seek and destroy a Reaper virus designed to enslave all non-Heretic geth.
Threat Assessment
The geth have considerable industrial powers, as one fleet consisted of anywhere between 5,000 and 10,000 ships of unknown armament. Also, one of their space stations (originally quarian, but extensively rebuilt later) was known to be over 20 km long and 11 km wide, which, despite the large amounts of empty space in it, is considerably larger than the stations constructed by the United Federation of Planets. That station was capable of generating a 1.21 petawatt transmission of considerable complexity. Their hacking abilities are formidable for any technologically dependent race that faces them. On the ground they deploy infantry that use a combination of mass accelerator rifles, flamethrowers, and rocket launchers, supported by tank-sized quadrupedal units called Armatures.
In space, their firepower is comparable to that of other Mass Effect civilizations, although they did build at least one "super dreadnought" a third larger than any other known dreadnought; this vessel had sufficient armor and shielding to withstand sustained fire from a quarian fleet attempting to destroy it (albeit with the support of the rest of the geth fleet). A surviving member of the Prothean race (generally shown to be more advanced than the current galactic races) stated its gun was a match for that of their flagship. It was stated that the geth built dozens of dreadnoughts, but it is unclear whether all were that model.
Nazara provided the Heretic Geth with the technology to turn organic beings into zombie-like cyborgs known as husks.