The Geth were created by the Quarians some 300 years before the events of Mass Effect. They were initially created as servants to their Quarian master for labor and war purposes. The Quarians slowly added more functionality to the Geth to allow them to do much more complex tasks. Through the extensive Geth network, the synthetics began gaining sentience, which greatly concerned the Quarians An attempt was made to disable the Geth but it failed. The Quarians panicked and began firing, at which point the Geth picked up weapons of their own and defended themselves. The resulting war (called the Morning War by the Geth) ended with the Quarians' defeat, and they were driven off their planet.
The closer the Geth are physically to each other, the more intelligent they individually become. An individual Geth has only a basic intelligence equal to what we would consider animal instincts, but when they are found in groups they can reason, analyze situations, and use tactics and do things that other intelligent races can do as well. They essentially share their brain power with each other, creating a neural network allowing for more complex abilities. During the time after the Morning War, the Geth gave themselves a new goal: build something that would house every Geth program.
300 years after the Morning War, the Reaper Sovereign sought the assistance of the Geth in starting the Reaper invasion. Sovereign promised the Geth technology that would bring them closer to reaching their goal if they helped in taking the Citadel. Two Geth factions were created with opposing views on the offer. The "heretics" were Geth that agreed to follow Sovereign, and the other Geth were those who wished to pursue their goal on their own without aid from others.
Types of Geth
The Geth models collectively dubbed Hoppers by Alliance forces are electronic warfare platforms. They can project electromagnetic radiation across a broad spectrum as an offensive weapon. They can also perform cyber warfare attacks against the onboard computers of body armor hardsuits and weapons, adversely affecting their performance.
The structure of Hoppers’ consists of an advanced and highly elastic artificial muscle material. This allows a hopper to compress its entire body for powerful leaps. Hoppers also have thousands of molecule-scale barbs on the surface of their hands and feet, which are used to cling to walls and ceilings. Hoppers are very difficult targets, leaping from one surface to another in rapid succession.
The Quarians have no record of any Geth models similar to Hoppers. The Geth must have developed this new morphotype over the last three-hundred years. This is troubling proof that the Geth are continuing to move towards technological singularity. Experts in synthetic life are intrigued that Hoppers appear to be even more organic than the baseline Geth.
They are weakest against Biotics, but due to the utilization of advanced stealth technology, they are resistant to tech abilities. The identified subtypes of Hoppers have been codenamed the Sapper, the Stalker,and the Ghost.
The Sapper is a stealth unit that resorts to wall jumping and radar jamming (lv. 3) in order to flank its opponents. It will attack with either a radiation burst which does toxic damage (slows healing) or a sabotage beam which overheats weapons.
The Stalker is a revamped version of the Sapper. The Stalker also resorts to wall jumping and radar jamming (lv. 7) in order to flank its opponents. It attacks using sabotage beam which over heats weapons, damping beam that resets Tech/Biotic abilities, overload beam that deals direct damage to shields.
The Ghost is a sniping unit; its dark color makes it hard to spot in the shadows. The Ghost can wall jump and uses radar jamming (lv. 5) to shield its position. It attacks using sniper beam that deals direct health damage, and overload blast is an area attack that deals significant damage to shields.
The Basic Trooper uses the Geth assault rifle as its main attack and uses barriers and shield boost for defense.
The Shock Trooper is a revamped version of the Basic Trooper. It weilds heavy armor and can shoot carnage blasts. The Shock Trooper has the ability to set barriers and initiate shield boost.
Although redundant, Rocket Troopers are much like basic Troopers, except they are red tinted and use rocket launchers. They can fire two main types of ammunition, disruption rockets are a heavy area attack that travel less than a hundred meters, and scram rockets that are a light area attack that travel one to four hundred meters.
The Sniper, on higher difficulty, can dish out one-hit kills. They use a sniper rifle for offence and radar jamming (lv. 1) for defense.
Heavy Troopers are bipedal Armatures (to the layman), two legged tanks. They are heavily armored and sport large weapons. Despite their size, they still move quickly gaining speed the longer they run, and they charge often.
The Destroyer is a good in combat, but is weak to tech attacks. Destroyers are similar to the Krogan; they utilize abilities such as carnage and can melee while charging.
The Juggernaut is a mix between the Rocket Trooper and the Destroyer. The Juggernaut can fire two rockets for every reload. The rockets fire short range and deal heavy damage to an area.
The Prime is a master in combat (lv. 6) and boosts combat abilities of all Geth in range. The Prime utilizes radar jamming (lv. 9), overload which depletes shields, damping which resets Tech and Biotic abilities, barrier which produces a shield, and shield boost.
Armatures are quadruped all-terrain heavy weapons platforms, a type of quadrupedal tank, akin to the armored fighting vehicles of other races. Geth being synthetic intelligences, armatures are not crewed vehicles, but intelligent entities, capable of independent decision-making and learning.
Armatures are equipped with heavy kinetic barriers. Their main cannon mounted on the articulated head turret appears to be a highly efficient conventional mass accelerator. It is capable of firing anti-personnel and anti-tank rounds. Some armatures carry drones into battle, presumably for reconnaissance purposes. Other host a swarm of insect-sized repair microbots.
The Armature maintains a blue hue and fires a siege pulse that deals heavy damage to a medium area.
The Colossus has a white outside and is nearly three times the size of an Armature. The Colossus can fire a siege pulse that deals massive damage to a large area.
Drones are flying Geth units. Drones use Mass Effect Fields to levitate; this makes them impervious to Biotics. Drones are susceptible to Tech attacks. They perform a variety of tasks from combat and recon, to repairing other Geth units.
The Recon Drone provides information about enemy whereabouts to Geth troops. It can fly over barriers to flank units, and attacks with a light turret. It has light armor and poses little threat.
The Repair Drone’s main directive is to repair other Geth units. It has little armor, and uses a low powered attack.
The Assault Drone, a flying tripedal, favors offence through flanking and providing cover fire for Troopers. It has better armor than the Recon Drone, and attacks with a heavy-revolving turret.
The Advanced Assault Drone is similar to the Assault Drone, except that it has more armor and less shielding. Some Advanced Assault Drones have more armor and more shielding. It uses the same heavy-revolving turret as the Assault Drone.
The Rocket Drone is an anti-armor Assault Drone, it fires disruption rockets. The rockets deal out heavy damage over a medium area.
The Advanced Rocket Drone is similar to the Rocket Drone, but third parties, such as Noveria security, and the Alliance (Luna base) use them.