Gō Koga

is a large and muscular man who resembles a punkish biker with spiky orange hair. Even without using his doll, Koga has impressive physical strength, able to easily overpower several Shinigami with just his bare hands. His doll is Dalk, a female metallic doll who can control her molecules and reshape herself at will. According to episode 83, Koga's original name is Claude Gauguin, and he lived in a European country in years past. He has lived for over 12 generations. After a falling out with Kariya over his plan to destroy Soul Society, which Koga found too extreme, Koga attempted to find and stop Kariya himself. He ended up fighting and losing to Tōshirō Hitsugaya instead, as neither he nor Dalk could contend with the extreme cold and long-range nature of Hitsugaya's Zanpakutō. He did not die, however, and was secretly taken by Yoruichi Shihōin to Rantao's home, where he was nursed back to health. Upon discovering that he was the last Bount, he apologized for the actions of his race, and Kariya in particular. He was last seen living with Rantao. No mention is made of Dalk's fate; however, considering that Bount are supposed to die with their dolls, it can be assumed that she either still exists in some form, or that Koga is merely an exception to conventional Bount rules, like Yoshino.

Doll
is Koga's doll. She takes the form of a metal sphere with the Bount seal upon it when sealed. When released, she forms into a rather flirtatious, semi-humanoid/spider-like shape and can control the metal that makes up her body, reforming it into any shape she wishes. She is able to split herself into tiny spheres no bigger than a ball bearing, making it very difficult to destroy her. She uses a variety of attacks in combat, such as creating metallic webs to entrap her opponent, firing pieces of her body as projectiles, and even turning her arms into machine guns to fire makeshift bullets through. After Koga drank the bitto's soul elixir, Dalk became even more spider-like, retaining only her humanoid torso. She also gained much more metal to work with. Dalk has trouble with cold-based attacks, which make it difficult for her to split her body apart. As a heavy, metal-based creature, she is also vulnerable to Izuru Kira's Zanpakutō, Wabisuke, which doubles the weight of anything it cuts. In contrast, Dalk seems to be nearly invulnerable to heat. It is revealed in episode 104 that Dalk's core form is a large battle axe that Koga wields. 

Trivia

 * He is the last surviving Bount in the series.
 * When he asks Yoruichi to tell Ichigo thank you, she completely forgets about it, due to the upcoming battle against the arrancar.