The Bounts (バウント, Baunto) are a group of humans that live by consuming human, plus Shinigami and Quincy souls which potentially increases their abilities.
Bounts are living beings just as Quincy are, but the difference being they have a special component that is encompassed by a human soul. Bounts absorb human souls, making them their own. It is these abilities that have named Bounts at various times in human history as vampires. As the accidental creations of a Shinigami scientist they were once affiliated with Soul Society. Currently the Bounts in general are only a small tribe of beings from what they once were. Due to their circumstance they are neither affiliated with Soul Society nor the living world, they are pariahs, accepted in neither dimension.
The natural abilities they possess due to their unique creation differentiate them from normal humans and even Qunicy. 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 Bounts
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 Bounts destroyed. Shinigami were dispatched to kill the Bount community, but a handful survived,
The Bounts who survived the massacre wandered like nomads and eventually fell prey to constant attacks by Hollows. dolls are the Bount equivalent to a Shinigami's Zanpakutō -. Regardless, the Bounts' leadership decided to gain access to Soul Society by means of the Quincys' power. The Quincy were unwilling to assist, and a battle ensued, in which the Quincy and Shinigami killed most of the surviving Bounts.
Soul Absorption: Bounts normally try to absorb the human's soul after the person dies and is trying to pass on. But they are also capable of taking the souls of those who are living, to do so kills the human.
Immortality: By absorbing human souls, a Bount can live forever. When they absorb human souls, they gain eternal life.
Empowerment: By taking the souls of living humans, Bounts gain unique abilities.
Dolls:Bounts, 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's 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 Bounts' 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 but Hiddan doll is merged with him by his special abilities). 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."
Bitto: Bounts are also able to create a unique form of dolls known as the Bitto. The are mosquito-like beings which drain the souls from humans and condense the energy into a purified liquid for the Bounts 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 elixor has been ingested, the Bount who took it immediately experiences the effects, with veins popping from their skin.