The Citadel

The Citadel is a massive space station located in the center of Citadel Space. It is the location of the Citadel Council, as well as the headquarters for various organizations and companies. It is located right next to the largest Mass Effect Relay currently still in use, and is a way station for various ships traveling the stars.

It is 27.8 miles in length (open), nearly 8 miles in diameter (open) and is estimated to weigh a total of 7.11 billion metric tons. There is a minimum population of 13.5 million inhabitants at anytime, not including The Keepers, and millions more who visit the Citadel daily for various reasons.

History
No one is truly sure where the Citadel comes from, though it is believed to have been built billions of years ago by an unknown race of beings as a either a death ship meant to conquer the universe or a central hub for an entire galactic empire, much like it is used today.

It was initially discovered by the Asari, who eventually brought other races within Citadel Space to it and established the Citadel Council. The Citadel Council quickly became the government of the various galaxies, bringing in over 50 other planets to their cause, dubbing them a part of the Citadel Collective. This idea soon expanded to organizations and businesses, being dubbed the Citadel Organization Collective.

The Keepers
When it was first founded as the Citadel Council's headquarters, maintenance was mainly done thanks to a variety of alien races hired as janitors, mechanics and maintenance workers. As the Council's influence grew and more of the station was used, it became apparent that this method would not work for long, and the Council sought alternatives. Lucky for them, one such maintenance worker found a hatch hidden on one level, revealing the hibernating place for a race they dubbed as The Keepers.

The Keepers are a race of bio-engineered insectoids that are completely docile and harmless. Upon opening the hatch and investigation crews being sent in, the chamber 'awoke' and the Keepers awoke as well. Startled, the response team was unsure what to do, but were almost instantly shown the docile nature of the Keepers, who after an unknown amount of time in hibernation, returned to the duty of maintaining and updating the Citadel.

Not much is known about the Keepers themselves, and due to their non threatening and docile nature, they are often times left alone by the vast majority of Citadel dwellers and visitors. Eventually, however, some got curious, antagonizing or even violently lashing out against them. This disrupted their flow of work, so the Citadel Council established a police for, known as The Judoon, giving them the task of protecting the Citadel, her interests, and the Keepers themselves.

The Judoon
After the discovery of the Keepers, tensions grew between the Citadel Council and their workforce, much of which was suddenly out of the job thanks to this race of insectoids and the Citadel Council's decision to let them do all the work. Worried they would have riots on their hands to deal with, and with growing issues on several planets under Citadel control, The Citadel Council established the Judoon Force, a police force made up of mostly Judoon.

The Judoon are a race of humanoid rhinos who approached the Citadel from an unknown location. Claiming their planet was destroyed by a clone race called the Sontarans, the Judoon presented themselves as a heavily organized race, having built their government around a successful police state. Upon giving them a new purpose, The Judoon dismantled some of their massive space ships to build a space station near the Citadel, and became the official policing force under the Citadel.

While most of the officers themselves are of the Judoon race, they employ other races for various other means. They allow peoples of all races to apply for employment, though have shown some favoritism towards Salarians and Ood. The Salarians offered them their hyper intelligence in the fields of medical science and weapon manufacturing, while the Ood are primarily a slave race, offering their calm natures and ability to communicate with multiple races to help the Judoon, who have often been referred to as intergalactic brutes.

The Judoon had some troubles at the start, mainly due to a lack of leadership. To help with this situation, The Citadel Council appointed a chief of police named Commander Tybo. Commander Tybo was the former captain of the 1005th Judoon guard on their home planet, and took over for the original leader elected by the Judoon who was killed in a firefight that broke out on the Citadel. Unlike most Judoon, Tybo spends more time indoors and in his office, content with not losing his life in the line of duty and sending orders to others.

Thanks to the near infinite wealth of the Citadel, The Judoon have been able to help police the universe with great success. While individual planets have police forces and their own military, the Judoon have jurisdiction over them all, able to tap these resources as needed for either information, bodies, weapons, or whatever they might need for an investigation or situation.

The Spectres
While the Judoon proved successful as a police force, the Citadel Council came to the conclusion that while they are an effective force for good, there is still more that can be done. They established a program to try and find some of the best warriors the galaxy had to offer that they could have at their disposal, calling these individuals Spectres.

These individuals, chosen specifically by the Citadel Council, and eventually other Spectres, Spectres were those who prove themselves worthy warriors in the face of almost certain death. Thanks to the vastness of the universe the Citadel operates in, they were able to find hundreds of possible candidates. Due to this, they decided that only a finite number of individuals would be allowed the title of Spectre, eventually settling for twelve.

The Spectres are the Citadels elite guard, able to act above the law and do whatever is needed to keep the Citadel safe. They are chosen for their combat skill, loyalty, previous accomplishments, and other contributing factors, making the selection process long and often times tedious. They are under oath to obey the wishes of the Citadel, they are sworn to not betray the Citadel or other Spectres, and have the go ahead to do whatever they feel is necessary. When one member dies or goes against the Citadel's wishes, the Council and Spectres choose a replacement. The Spectres rarely work as a team, usually completely their own agenda while waiting for missions of orders from the Citadel.

The Sontaran War
The Citadel remained relatively untouched by conflict for many years, thanks in part to the Citadel's leadership over the various planets under their control and with the help of the Judoon and Spectres. However, that does not mean the Citadel has had enemies over the years.

With countless terrorist threats, anti-Citadel activists, and various other crimes conducted to show defiance to the Citadel, there was one enemy they didn't think they would have to face; the Judoon's old enemy, the Sontarans.

After destroying their planet, it was revealed that their intention wasn't simply to destroy the Judoon planet, but to destroy the Judoon themselves thanks to a long standing rivalry that goes far back, no one knows who threw the first punch. The Sontaran's declared war on the Citadel and its allies, and this led to a massive war, spanning several years and millions of casualties on both sides.

The battle was nearly endless thanks to a wormhole the Sontarans had created allowing them to jump from their universe instantly to the Citadel. With this, they are able to clone new soldiers quickly and get them into the battle faster than ever before. The Citadel brought all their best science officers together to try and figure out a plan, eventually coming up with a suicide mission. They will send in a volunteer to go through the wormhole and detonate a weapon of immense power.

Though it was never confirmed, the war was ended when a volunteer comes forward calling himself The Doctor. He claims to have had experience with the Sontarans before, and he will try to convince them to surrender rather than straight out kill him. He gets into his ship, which looks like a blue police box from ancient Earth, and enters the wormhole. Minutes later, the wormhole implodes, leaving only a fraction of the Sontaran fleet remaining in this dimension.

While that is the story that many feel is true, the Citadel claims that the Sontarans simply surrendered to the might of the Citadel. They banished the remaining Sontarans to another dimension, making sure they are never allowed to return to their universe again.