The Gradin Belt is a large region of the Delta Quadrant several thousand light-years in diameter approximately 40,000 light years from Federation space. It is connected to the Alpha Quadrant by the Barzan System (Alpha Quadrant) ninety-one days by way of the Barzan Wormhole. Of all of the areas in which Starfleet operates, this one is the most well-explored and well-studied. It is a confluence of many different advanced powers and so is currently a diplomatic hotbed.

History

Initial Discovery

In 2375, the USS Voyager first discovered the Gradin Belt when it passed through and destroyed a subspace vortex controlled by the Malon Cooperative. For the next three years, it travelled through the Gradin Belt and made first contact with dozens of species including, most notably, the Devore Imperium, the Hierarchy, the Turei Alliance and the Vaadwaur. The USS Voyager moved through the Gradin Belt at impressive speeds thanks in part to access to alien technology that was superior to its warp drive. This region would be the last part of the Delta Quadrant it would journey through before leaving in 2378. As a result of these "jumps" areas of the Belt have not been properly explored. Starfleet would not return to the Gradin Belt again for over a decade.

Rediscovery

In late 2388, researchers discovered an aperture for the wandering Barzan Wormhole in the uninhabited Epatha System, near to the Kadi. While it was initially unstable, a science vessel was able to help stabilize this aperture of the wormhole, in combination with one in the Barzan system and another ship past the Nekrit Expanse. Presently, this connection allows supplies and ships to transit back and forth on a regular basis.

There are no major Starfleet facilities besides a relay station, operated jointly with the Kadi, at the mouth of the Barzan Wormhole in this area of space, nor are there any Federation colonies. Starfleet, along with other Alpha and Beta Quadrant governments are not allowed to expand into the Delta and Gamma Quadrants due to the Jankata Accords.

Species and Lifeforms

Major Powers

Borg Collective - A cybernetic pseudo-species made up of thousands of assimilated species, Borg space abuts the Gradin Belt; however, a turbulent phenomenon known as Chaotic Space acts as a sort of natural barrier mostly protecting the Belt from the Collective.
Devore Imperium - A xenophobic and authoritarian culture, the Devore Imperium lays claim to a large swath of the Gradin Belt. It protects its borders with a strong military presence and inspects all who wish to pass through their space, harboring a particular aversion for telepaths.
Hierarchy Central Command - The operating authority for the Hierarchy, Hierarchy Central Command is highly stratified militaristic interstellar power technologically on par with Starfleet. It lays claim to a region of the Gradin Belt that it protects strictly and from which it conducts espionage and occasional raids against other inhabitants of the Gradin Belt.
Hirogen - A largely nomadic species, the Hirogen are occasionally found hunting "prey" in the Gradin Belt. Following their encounters with the USS Voyager, a small alliance of Hirogen has begun to seek an end to their nomadic lifestyle, forming colonies, establishing a space station, and claiming a region of territory on the edge of the Gradin Belt as their own.
Malon Cooperative - An advanced and economically-motivated culture, the Malon inhabit a region of the Gradin Belt. While they frequently trade with other regional powers, they have thus far shown no interest in interacting with Starfleet on account of their interactions with the USS Voyager over a decade past.
Turei Alliance - Born originally to defeat the Vaadwaur and later maintained by a shared desire to use the Underspace for their own purposes, the Turei Alliance considers themselves at war with the Vaadwaur survivors, fearful that the return of the Vaadwaur will weaken their reach and cut off their economies. The Turei pushed for a mutual aggression pact and settled for a non-aggression pact with the Federation, outlining the Vaadwaur as a common threat.

Minor Powers

Vaadwaur - The first species known to have mapped the Underspace, the Vaadwaur used it to control massive swaths of the Delta Quadrant in antiquity. Almost a thousand years ago, the Vaadwaur were defeated by the Turei Alliance. Believed extinct until 2376, the Vaadwaur have since begun to move quietly again, their motives not fully understood, although many in the Gradin Belt fear that they will eventually attempt to retake control of the Gradin Belt and their former territories.
Monean Maritime Sovereignty - A regal union led by forty-seven regional sovereigns, all of whom sit on the Sovereign Council, live on a unique planetoid that was made completely from water. In 2375 their home was under threat of dissipation, eventually the Sovereign Council agreed to make significant changes to preserve their world, but they also began colonising other nearby planets that had large bodies of water.
Qomar Planetary Alliance - A xenophobic interstellar union that is one of the most technologically advanced governments in the region. They are not xenophobic based on conflict with others, but simply down to the fact they believe due to the high level of technological development they are superior to other species as well. Rarely do they engage with other species. Their alliance is formed only by colonies established by the Qomar.
The Antarian Pact Organisation - A loose peace treaty among five races (Antarians, Aksani, Chessu, Imhotep and Terrellians). The Pact was mediated by the Antarians who had remained neutral in the conflict between the Aksani, Chessu, Imhotep and Terrllians. All four races had suffered from the war with one another over a long period of time. The pact was formed in the 2370s. To celebrate the recent peace, in 2377 all five species came together to race in the Antaraian Trans-stellar Rally. It was a chance to put aside all animosity, and for the signatories to come together in a spirit of peace and friendly competition. After its first initial success the rally became an annual event which attracted the attention of other non-pact members to be involved with it.
Ba'neth - A xenophobic non-humanoid race that has some of the most advanced cloaking technology ever encountered by the Federation. The Ba'neth have worked hard for decades to keep their existence a secret from others. They are quick to assess other races and ensure that any evidence of themselves is erased.
Annari Empire - An aggressive and sophisticated power that uses a combination of diplomacy and military strategies to annex worlds into its empire.
Chokuzan Republic - A federal constitutional republic that has many members as part of its union. The species has a high moral code on behaviour that they expect their citizens and visitors to adhere to. Technologically advanced, the Chokuzan fleet is equipped with standard weapons like Starfleet ships, but they also have other forms of weapons including one that inflicts bodily harm to an attacking ship's crew.

Noted spatial anomalies

For a region of space filled with a range of lifeforms, the Gradin Belt is also filled with interesting and unusual bodies. As a result, some of these anomalies have protected many races in the Gradin Belt from the nearby threat of the Borg Collective from expanding. These include, but are not limited to:

The Void Radiation Field - Named by the Voyager crew due to the high levels of theta radiation and the fact the region is in complete darkness due to this, it was later discovered that a Malon crew were responsible for all of this. Voyager stopped the Malon crew in hopes of saving the native species. A vortex also existed in the region, but this was collapsed by Voyager in 2375.
Subspace Sandbar - A region of space that borders near to the Devore Imperium and Borg claimed space. It intersects between space and subspace and as a result Voyager discovered it also a place that crossover into a transdimensional realm inhabited by photonic lifeforms.
Telepathic Pitcher Plant - A huge space-dwelling bioplasmic organism that could create a neurogenic field that extended several million kilometers and could manipulate most races in entering it. Its sole purpose was to consume the antimatter and biomatter. After escaping the organism, Voyager left warning buoys on the edge of the field to prevent other starships.
Chaotic Space - Acting as a natural barrier from preventing the Borg from invading and assimilating a large collection of races, this large phenomena is a huge navigational hazard. The laws of physics were consistently changing and it is rare for ships to leave it once in.
Class T Cluster - A small nursery of bodies that contains a range of spatial anomalies, however this particular one that exists close to the Qomar Planetary Alliance and the Antarian Pact Organisation, is also home to dark matter lifeforms.
Temporal Spatial Rift - An unusual phenomena that exists in all planes of the spacetime continuum, a high levels of neutrinos and chronitons exist within it which can send out discharges of chronokinetic surges. Again Voyager left behind warning buoys to prevent others from being trapped by it.
The Void Rift - An enclosed inert layer of subspace that can cause graviton funnels to pull ships in, it has trapped many species within its small confines. The only thing that can exist in the Void are ships. There are no traces of sources of power, in fact the anomaly drains energy from ships as well.

The Gradin Belt in Play

Compared to other areas of interest in the Delta Quadrant, all of the powers in this space are roughly equal to (and in some cases superior to) the Federation in terms of technology. None of them are as large as the Federation, but since the Federation is very far away and only connected to this area of space once every three months, Starfleet ships in the area are protected by the promise of likely Federation intervention if they're attacked more than any real military power being deployed. In other words, the Federation flag would protect you, to a point, but you're very far from reinforcements if things do go south.
The Starfleet ships stationed in this area of the space have largely been tasked exploring diplomatic and trade opportunities within the region, as well as keeping the peace as far as the prime directive allows. It is in the Federation's interests to keep this area of space from turning into a firestorm to let it serve as a check against Borg expansion, as their space lies just beyond this area.
This is the area most frequently explored by non-Federation Alpha Quadrant species such as the Ferengi, who are also looking for trade opportunities.