Bount

The Bounts are a group of humans that live by consuming human souls, which potentially gives them everlasting youth. For this reason, they are often compared to vampires. During the series' anime-exclusive Bount arc, the Bounts collectively serves as it's main antagonists, especially their leader, Jin Kariya, who serves as Aizen's temporary replacement.

History
The Bounts were created by Ran'Tao as the accidental result of an explosion during an experiment by the predecessor to the Seireitei Technological Institute. The experiment was an attempt to develop eternal life using the already slow-aging shinigami souls as the base, but the materials used in the experiment crossed with the development of souls in the real world and led to the creation of a new spiritually-active human race, the Bount.

The Bount souls were scattered about the world, giving rise to a new race that never aged after reaching their twenties or thirties. They were generally treated as outcasts due to the fact that they did not age. The shinigami scientist responsible for their creation, Ran'Tao, gathered most of the Bount into a small community in a secret cave structure, several centuries before the main storyline. It was her intent to improve the quality of life for the people whose suffering she felt responsible for.

However, the embarrassment of this accidental creation, as well as the fact that a tenth of Seireitei was destroyed in the resulting explosion and the possible threat they posed to the balance between the worlds, led the Chamber of 46 to rule that the experiment and its failure was to be covered up, and the Bount destroyed. Shinigami were dispatched to kill the Bount community, but a handful survived, including a young boy saved by Ran'Tao herself, to whom she gave a seal that would help unlock the Bounts' true power.

The Bount who survived the massacre wandered nomadically and eventually fell prey to constant attacks by hollows. It was during this time that the boy, who would later become known as Eugene, activated the seal's power and merged with his doll - the Bount equivalent to a shinigami's zanpakutō - and killed off the attacking hollows. The survivors eventually found refuge in another cave and began devising a plan to return to Soul Society, which they saw as more of a home than the real world ever could be. Eugene, now an adult, was against this plan. He had witnessed the massacre and believed the only thing that would await the Bount if they returned to Soul Society would be subservience or death. Regardless, the Bount leadership decided to gain access to Soul Society by means of the Quincy's powers. The Quincy were unwilling to assist, and a battle ensued, in which the Quincy and shinigami killed most of the surviving Bount.

Further infuriated by this, Eugene took the last few surviving Bount, all of whom were of a similar mindset to him, and began plotting revenge on Soul Society. These Bounts managed to perfect the control of their dolls, and by the time of the main storyline Eugene, now going by the alias, Jin Kariya, was ready for vengeance.

Powers
The Bounts's inability to age is a product of how they survive: consuming human souls. This gives them potentially everlasting youth so long as they can find souls to consume. This also seems to make them infertile, as only one Bount, Yoshino Sōma, had the ability to reproduce out of the entire species. Normally, Bount consume human souls that have already died. Under the leadership of Jin Kariya, however, they began consuming living souls. Consuming living souls causes a Bount to physically age to a small degree ; the only person to have consumed enough to have noticeably aged is Sawatari, who appears as if he is well into his eighties while normal Bount retain an appearance of someone in their twenties or thirties. It is not known if a Bount could also die this way.

Dolls
Bount, being created as variations on a shinigami soul, have similar powers to shinigami. The foremost of these powers is the Bount doll, a familiar equivalent to the shinigami zanpakutō. Like a zanpakutō, a doll is its creator's power given physical form. Also like a zanpakutō, a doll's personality is much like its creator's, though the dolls seem to have more personality variation than the zanpakutō spirits seen thus far.

The main difference between a doll and a zanpakutō is how they operate. Unlike a zanpakutō, whose personality is generally dormant except when the shinigami wishes to speak to them, a doll's personality is always dominant. Dolls are self-sufficient when released, though they can easily be resealed. The Bount's ability to control their doll is largely based on their individual power and relationship with the doll. Moreover, if either the doll or its Bount partner sustains severe damage in a battle, the Bount may lose control over his doll, depending on the amount of damage dealt. If a doll is injured, it will simply return itself to its sealed state. However, should its master be injured, the doll may go berserk and kill its master, as Ugaki and Mabashi's dolls did. A doll may also kill a Bount who is not powerful enough to contain it, as was the case with Cain. Bounts with a genuine bond with their dolls can transgress this (but only if their interaction goes well beyond that of between master and slave), however, as shown by Yoshino's doll's loyalty towards his master to the point where he refused to leave her side to fulfill her final wish: for her to be merged with him

Like a zanpakutō, dolls are generally sealed into an object and released as necessary (Gō Koga's doll, for example, is sealed into a metal sphere). The object varies greatly from person to person and is often an expression of the doll's abilities. In order to call upon a Bount's doll, the phrase "Zeige Dich" is said, which is a German phrase meaning "Show yourself."

To summon a doll, a Bount needs to undergo a ritual where they chant an incantation. These instructions were first given to young Kariya by Ran'Tao after the shinigami attack. The ritual includes sulfur, phosphorus, carbon, water, fat, magnesium and lime (the ingredients of the human body). When a doll is summoned, it is small in size and power, but grows as the Bount's power grows.

Bitto
Jin Kariya and Ugaki were also able to create a unique form of dolls known as the bitto. The bitto are mosquito-like beings which drain the souls from humans and condense the energy into a purified liquid for the Bount to drink. They even produce a useful vial in their sacs to store the elixir (which takes the form of a red blood-like liquid). After the soul elixer has been ingested, the Bount who took it immediately experiences the effects, with veins popping from their skin. Kariya created the bitto by sacrificing Yoshino Sōma, the only Bount able to reproduce, in an elaborate ritual, producing a large swarm of them.

List of bounts

 * Ran'Tao - Creator, Incarcerated.
 * Jin Kariya - Leader, Deceased.
 * Gō Koga - last surviving Bount
 * Cain - Deceased
 * Hō and Ban -Deceased
 * Mabashi - Deceased
 * Ryō Utagawa - Deceased
 * Sawatari - Deceased
 * Ugaki - Deceased
 * Yoshi - Deceased
 * Yoshino Sōma - Deceased
 * Maki Ichinose - Deceased