Originally a greater daemon summoned by Rimuru Tempest, Beretta emerged to inhabit a custom-built golem body. This vessel replaced Ramiris's destroyed Elemental Colossus, binding Beretta to serve as her guardian for a century. Upon possessing the golem and receiving the name "Beretta" from Rimuru, the entity evolved into an arch doll. Though the initial contract was later annulled, Beretta chose to remain Ramiris's permanent subordinate while acknowledging Rimuru as a secondary master, gaining access to expanded powers and evolutionary potential. The initial golem form stood 180cm tall, featuring spherical joints and a mask reminiscent of Rimuru's design. Post-evolution granted Beretta long black hair (alternately described as silver or white), pale skin, crimson-glowing eye slits on the mask, and a more humanoid frame. Constructed from demon steel, the body retains a mechanical appearance. Lore consistently confirms Beretta's genderless nature, stemming from both the demonic origin and artificial construction. Beretta's personality reflects traits of the black demon progenitor Diablo, exhibiting high etiquette, intellectual curiosity, and fierce loyalty. The character maintains a calm, rational demeanor even in combat, displaying ruthless efficiency against enemies like Clayman's doll Viola. Beretta acts as a disciplinarian for the impulsive Ramiris, frequently scolding her recklessness while sharing her enthusiasm for researching magical artifacts and spells. Despite deference towards powerful entities such as Diablo or Guy Crimson, Beretta voices opinions candidly and without fear. Initial abilities centered on the unique skill "Contrarian," granting opposite attributes to adversaries and enabling simultaneous use of demonic and angelic powers. Rimuru's ascension to demon lord transformed the body into a holy demon puppet. Further evolution occurred in light novel volume 16 when Rimuru strengthened Beretta's soul, resulting in a chaos metalloid form—a supreme metal lifeform—and the ultimate skill "God of Machines" (Deus Ex Machina). This skill allows free shape-shifting into any metallic form and manipulation of machinery. Power progression spanned from A-rank (greater daemon) to special A-rank (arch doll) and finally S-rank (chaos metalloid). Key background developments include Beretta sensing Rimuru's entrapment by Hinata Sakaguchi and aiding Ramiris in exposing Clayman's schemes. During Walpurgis, Guy Crimson forced Beretta to choose a single master, resulting in exclusive allegiance to Ramiris while preserving indirect loyalty to Rimuru. Beretta later managed defenses in Ramiris's labyrinth as head of the Ten Bosses but relinquished this role during the Eastern Empire invasion due to excessive workload, transferring duties to Gadra. The character appears in spin-offs like "The Slime Diaries," which clarifies Diablo's absence during the initial summoning prevented him from becoming Ramiris's protector. Pronoun usage varies across adaptations: light novels employ male or gender-neutral terms, manga and "ISEKAI Memories" use male pronouns, while anime adaptations occasionally use female pronouns influenced by vocal performance and design. The author explicitly confirms Beretta's genderless nature. Naming trivia reveals "Beretta" derives from a firearms brand, deviating from Rimuru's typical car-themed demon names due to the golem's aesthetic evoking firearms. The character's visual design under the mask drew inspiration from Saber from "Fate," with the author requesting the same Japanese voice actress.