Deepground

This is not FF7 canon. Well, some of it is. Most of it is not. This is mostly me trying to keep my notes straight. Spoilers abound.

History
Established 1961 as the Midgar General Hospital- later known as the Old Midgar General- this building sat near the middle of modern-day Midgar. It was part of the Company Town built in the center of the eight surrounding villages. It was greatly expanded in 1966 shortly after the bombing of Kalm in order to accommodate all the wounded. Due to infection concerns, it was strictly quarantined.

In 1969 the SOLDIER program was launched at Midgar General’s research building. It started out innocent enough. The first successful live birth was a little girl named Rosso, born in 1970. She was followed by brothers Weiss and Nero born in 1971 and 1972 respectively. The three of them plus Azul the Cerulean later became the first of the colored Tsviets.

1979 saw construction begin on the Plate and the new Shinra Building; Midgar General and the old Company Town were built over. The medical facility is still there and remains operational. It is referred to as the “Deepground Unit” and functions as an intensive care/experimental treatment ward for those with mortal injuries/illnesses. Azul joined Shinra during the start of hostilities with Wutai in 1982. Deepground was subsequently expanded to accommodate all the wounded from Wutai as well as what began as a ward for POWs. Things got officially Squicky as POWs and then mortally wounded soldiers were conscripted for experimental treatment.

Restrictors
The so-called "Lost Unit" was a unit of infantry who were lost behind enemy lines during an unnamed conflict (not Wutai) for over a year. When they were finally rescued, only four remained alive, all of them badly scarred physically, mentally, and emotionally. They were given mako and Jenova as therapeutic treatments since nothing else seemed to help. While the men gradually returned to a calmer state, what no one realized was that Jenova had more or less simply taken over the minds of these broken men and was puppeting them for her own purposes. As the men recovered and their strength returned, it was obvious something was off. However, they seemed stable and they had been through hell, so no one said anything. No one remembers their names, but the troops refer to them by nicknames behind their backs:

"Doc"
The Restrictor in charge of the Medical facility. Besides general medical treatment of all who live around Reactor Zero, he is responsible for:
 * The Breeding Program and the Mothers and children under five years old
 * The medical aspects of the Tsviet program

"Professor"
The Restrictor in charge of the Deepground Science Department (yes, they have one too).
 * Jenova research
 * Hybrids (aka: mutant creatures)
 * The technological end of Weapons Development

"Sarge"
The Restrictor in charge of all things Military.
 * The combative aspects of the Tsviet program, particularly the colored Tsviet officers
 * The combat side of Weapons Development
 * Training troops, including new recruits and children over five years old

"Warden"
The Restrictor who brings in new blood/fresh meat, depending on how you look at it.
 * Requisition of new recruits (ie: kidnapping)
 * Orientation (kiss your humanity goodbye)
 * Placement (this is the totem pole. you are not on it.)
 * General Maintenance (here's a toothbrush. start scrubbing.)

No one is quite sure how Deepground went from an intensive care ward to a military testing facility, but it is agreed that the Restrictors had a lot to do with it. They became department heads over the workers and patients, treating them more like soldiers. When the Tsviet program was instituted, that was the last nail in the coffin as far as Deepground being a place for rest and recovery. It became a faceless guard factory utilizing a variety of unethical techniques to breed super-soldiers. The most notable method is the infamous Breeding Program in which any women able to bear children are essentially made into breeding stock. Many of them die before giving birth, most of those who do carry to term die shortly thereafter. No woman lives to deliver more than one child (unless she has a multiple birth), and if she survives, she is transferred into combat ranks as a "JANE" (Jenova Augmented Natal Exemption) and taught to fight. In order to keep non-Restrictors in line, microchips are implanted into each captive. While these chips do not make slaves of the wearer- they have mental conditioning (brainwashing) for that- it does keep them from raising a hand against their captors and from running away.

The Restrictors- or rather, Jenova's commands- are the source of the brutality that has made Deepground famous as an urban myth. To Jenova, death means more life energy to feed on. The daily slaughter of troops and Mothers is not a negative thing in her mind, it's just lunch. While the cheapness of human life wears on some like Azul or Argento, to others such as Rosso, Weiss, and Nero, that's just the way it is.

JOEs
Jenova Operative Elite

Exclusively male, these soldiers are best described as "flesh robots". A combination of training, brainwashing, and the microchips implanted upon their "enlistment" (read: capture) help to erase any free will they might have had.

JANEs
Jenova Augmented Natal Exemptions

Exclusively female, these are women who cannot bear children. Some of them are former Mothers, though most entered Deepground by other methods ( injured soldier, prisoner of war, criminals, kidnapping, etc.). The only reason these women fight is because they are useless to the breeding program. Like their male counterparts they are slowly stripped of their personality until the only thoughts in their heads are Jenova's.

Tsviets
Tsviets are the elite of the elite, soldiers too intelligent and promising to be fully subjected to the brainwashing that most are given. Because of the physical demands of combat- and Jenova's incompatibility with women- the vast majority of Tsviets are male. Tsviets designated by color are the most skilled and most deadly of this already elite class. So far there are only four, and only one of them is a woman:
 * Azul the Cerulean
 * Rosso the Crimson
 * Weiss the Immaculate
 * Nero the Sable