Race: Shinigami

Brief Description:
Shinigami (死神, "death god(s)"; Viz "Soul Reaper(s)") are a race of spiritual beings that act as enforcers and psychopomps who all share similar supernatural powers. They are souls with a high level of innate Spiritual Energy, recruited from the ranks of the residents and nobility of the Soul Society. Like all spirits, they cannot be detected by normal humans. Shinigami use their Zanpakutō, supernatural swords that are the manifestation of their owners' power, to perform soul burials on Pluses. Shinigami also use their Zanpakutō as well as magic known as Kidō to fight their arch-enemies, the Hollows.

For further reading, you may look here:
Shinigami Wiki

Their World:
Soul Society (尸魂界 (ソウル・ソサエティ), the Japanese spelling used literally translates to "dead spirit world")[1] is the afterlife (also called the spirit world). It is meant to correspond to Heaven or Nirvana in Human belief systems. It is the place where most departed souls and the Shinigami dwell. Currently, the Soul Society has been cut off from the other worlds. They have no access to the Gensei, or Hueco Mundo.

[color=white]Within Their World:[/white]
Seireitei (瀞霊廷, court of pure souls) is in the center of Soul Society, a circular shiro with four main entrances, each guarded by a Gate Guardian. The walls of Seireitei are made of stone called Sekkiseki (殺気石, spirit reducing stone), a material known to negate all Reiryoku, similar to magnetic lodestones. The stone also forms a spherical barrier around the city which stops anything spiritual from breaching it.

Rukongai (流魂街, wandering soul city) is the largest portion of Soul Society and the most populated. It is divided into 320 districts (80 in North Rukongai, 80 in West Rukongai, 80 in South Rukongai, 80 in East Rukongai). Rukongai has recently been under attack by wandering hollows. As far as the Shinigami can tell these are random attacks meant only to feed, and only occur in the outer 10 districts. They are quickly silenced by Shinigami sent out to protect.

Shinōreijutsuin (精神的な芸術アカデミー, Spiritual Arts Academy), sometimes called the Shinigami Academy, is an institute founded by Genryūsai Shigekuni Yamamoto. Located in Seireitei, the academy trains future Shinigami for each of the three military arms of Soul Society.

For more reading, you may look here:
Soul Society Wiki

The Hierarchy:
Soul Society is ruled by a king. He commonly leaves the running of Soul Society to the Central 46 Chambers and Nobles. He lives with his family in the Royal Palace in a separate dimension in the very core of Soul Society, which is protected by the Royal Guard. The King does have a specific system of "speciality duties" which are actively carried out but the exact nature of these duties is unknown.[4] The dimension can only be opened with a tri-pronged golden key fittingly named the Royal Key (王鍵, ōken).[5] The location of this Royal Key is passed down verbally from one Gotei 13 Captain-Commander to the next, the current holder being Genryūsai Shigekuni Yamamoto. According to Rangiku Matsumoto, no Shinigami has ever seen the king.

Central 46 (中央四十六, Chūō Shijūroku): The Central 46 serve the Shinigami royalty (the ruling class of all Soul Society). They are made up of 40 wise men and 6 judges, selected from all of Soul Society. They are sealed into an enclave in Seireitei called Seijōtōkyorin (清浄塔居林) which no one else may enter, regardless of their military or civilian status. They act as a supreme judiciary organization whose authority puts it in direct control of the legal system. They handle all rulings on Shinigami and souls who have violated prohibitions. Their orders are absolute and no decision has been known to be overturned.

The Gotei 13 (護廷十三隊, Goteijūsantai; 13 Division Imperial Guards, 13 Court Guard Squads in the English dub, 13 Court Guard Companies in the English manga) is the primary military branch of Soul Society. It is also the main military organization that most Shinigami join after the academy.

Division 1: No special duties have been noted for the 1st Division. The First Division is ranked highest among the 13 Divisions. Even subordinate members of the First Division are considered model Shinigami. Emergency must be dealt with swiftly; quick decisions and quick actions are essential. The division is able to ascertain a situation and mobilize quickly even before an order is issued. That is the true value of the First Division

Division 2: The 2nd Division has been directly linked to the Onmitsukidō for well over 110 years ago by former Captain Yoruichi Shihōin who was Commander-in-Chief of the Onmitsukidō before being promoted to a Captain. As such the special operations of Soul Society has become the full measure of what the division involves itself in primarily. Members are tasked with assassination, policing, detention and message couriers.

Division 3: No special duties have been noted for the 3rd Division. However, in the current situation, they have been tasked with surveillance of the first 10 districts, closest to the Seireitei.

Division 4: The 4th Division is the medical/supply division. They are responsible for both treating the injured and doing most of the manual labor, such as cleaning the Seireitei. The 4th Division is further divided into teams that have specific assigned jobs. Other division members use their spiritual power only for fighting. Members of the 4th Division possess spiritual powers that is used to tend to wounds and provide relief. They use these special powers and the benefits of their daily training to act with precision and speed to aid injured comrades. 4th Division administers emergency first aid to injured division members and transports them to the General Emergency Relief Station.

In addition, the nurses who work in the Sōgō Kyūgo Tsumesho (綜合救護詰所, the coordinated relief station) have special Shihakushō (死覇装, Garment of Dead Souls) that are pink in colour with hats that are reminicent of nurse uniforms of the Human World.

Division 5: No special duties have been noted for the 5th Division. The members of this division are all highly skilled, having been trained by a captain who excels at everything, including battle readiness. Because of this they are charged with protection of the Outer ten districts in the current situation..

Division 6: No special duties have been noted for the 6th Division. The 6th Division is seen as a model division by every Shinigami and is known for its strict adherence to rules. In the current situation they have been charged with protecting Districts 20-29 of the Rukongai.

Division 7: No special duties have been noted for the seventh Division. This division is made up of sincere, unpretentious people who live life with gusto. Since the sealing of the Gensei, they have been charged with protecting Districts 30-39 of the Rukongai.

Division 8: No special duties have been noted for the eighth Division. Since the sealing of the Gensei they have been charged with protecting Districts 40-49.

Division 9: The mission of the Ninth Division is to protect the Seireitei. It is always on standby for combat because it is the security force of the Gotei 13. Traditionally, Ninth Division has overseen arts and culture. For this reason it is known to be in charge of the Seireitei news magazine. All the lieutenants of the divisions of Gotei 13 hand in their reports to them.

Division 10: No special duties have been noted for the 10th Division. They have been charged with the task of protecting Districts 50-59.

Division 11: The Eleventh Division is the direct-combat Division with a specialization in swords-only combat, forgoing the other Shinigami arts and thereby being one of the most specialized divisions in the Gotei 13. The division's doctrine of dominating in battle is what appeals to its members; they believe that fighting is what makes life worth living. This is what separates 11th Division from the others and makes them the strongest division. Everyone in the 11th Division are highly skilled in fighting. They believe if they are going to die anyway, go down fighting gloriously.

The division is also setup so that to become the Captain of the Eleventh, the candidate must do so through the third method of becoming a captain, killing the previous captain in front of 200 members of the Division, which is almost the entire Division.[4] Upon defeating the previous Kenpachi, the new captain takes on the name of Kenpachi or the best swordsman of each generation. Since the rise to captain status of the current Kenpachi, an unofficial rule has been added that says to be a true member of the Eleventh Division, one's Zanpakutō must be a melee-type.

Recently they have charged with the task of defending Districts 60-69.

Division 12: The 12th Division develops new technology and spiritual tools and its been the home of the S.R.D.I. for 110 years.

The 12th Division has been directly linked to the Shinigami Research and Development Institute over 100 years ago by former Captain Kisuke Urahara. As such technological and scientific research has become the full measure of what the division involves itself in primarily. Members are tasked with research and collection of data and samples, something both the current and previous Captains are very enthusiastic about, though not to the same extreme.

Division 13: No special duties have been noted for the 13th Division. Since the sealing of the Gensei they have been charged with the task of defending DIstricts 70-79.

For more information you can check here:
Gotei 13 Wiki

Their Powers:
Zanjutsu (斬術, Swordsmanship; Viz "Art of the Sword"; Cutting Technique) is the most used form of combat among Shinigami. As the name suggests, it involves using a Zanpakutō and its various special abilities to attack an opponent. In addition to its basic form, each Zanpakutō has two enhanced forms: Shikai (始解, Initial Release) and Bankai (卍解, Final Release), which change the sword's form to unlock its potential and that of its user.
-The Shikai (始解, Initial Release) is the second form (or first "upgraded" form) available to a Zanpakutō. To activate it, the Shinigami needs to learn the name of their Zanpakutō. This is not as easy as simply picking a name, as the living spirit of the Zanpakutō already has its own name. Therefore, the Shinigami must be able to communicate and harmonize with their Zanpakutō effectively, which requires being able to speak to the spirit within its world.
-The Bankai (卍解, Final Release) is the second and final upgraded form of a Zanpakutō. To achieve Bankai, one must be able to materialize and subjugate their Zanpakutō spirit. Materialization means the opposite of getting dragged into the Zanpakutō's inner world. Instead the wielder needs to summon the Zanpakutō's spirit into the physical world. It usually takes 10 years or more to achieve, plus the experience needed to master it.

Kidō (鬼道, "demon way", or "spirit way" sometimes translated as Demon Arts; Viz "Soul Reaper's powers"; "Spells") is the technique that Shinigami use to focus their Spiritual Energy into a wide variety of magic spells that can serve many purposes, such as healing, defense, or combat. According to Sōsuke Aizen, it is one of the four basic Shinigami combat forms.

List of Kido: Kido Wiki

Hakuda (白打, "Hand-to-Hand Combat"; lit. white hits) is the general term for close-combat techniques that make use of one's own body as a weapon. High-speed Taijutsu (体術, Body Skill) attacks are used to overwhelm the opponent. Physical strength and skill is determined by this class. It also seems to be a combination of several martial arts.

The foremost practitioners of this technique are those assigned to the Onmitsukidō.

Hohō (歩法, Agility; Viz "Fast Movement"; lit. step method) is an important skill for most Shinigami. The agility and speed of Hohō can be enhanced and improved through mastery of it, concentration, and training. The foremost practitioners of this technique are those assigned to the Onmitsukidō. Shunpo (瞬歩, Flash steps) is the most commonly used Hohō technique. However, there are variations even within Shunpo and other Hohō techniques that only master Hohō practitioner can use.

Their Weapon:
A Zanpakutō (斬魄刀; literally, soul-cutter sword) is the main weapon of the Shinigami, the Arrancar and the Visored. The art of wielding a Zanpakutō is called Zanjutsu (斬術; literally, swordsmanship).

For more Information, click here:
Zan Wiki