Info on bounts

The Bounts' 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, Bounts 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 Bounts retain an appearance of someone in their twenties or thirties. It is not known if a Bount could also die this way.

Dolls
Bounts, being created as variations on a Soul Reaper soul, have similar powers to Soul Reapers. The foremost of these powers is the Bount doll, a familiar equivalent to the Soul Reaper 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 Soul Reaper wishes to speak to them, a doll's personality is always apparent. 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 (Koga Gō'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 called, 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 Rantao after the Soul Reaper 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 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 elixir 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.