Beretta

In Volume 4, as an escort for Ramiris, Rimuru summoned a high-ranking demon into a magic steel doll he created, giving it the name and thus birthing the Archdemon Doll. It appears as a humanoid with long silver hair, red eyes, and a masked face. With Rimuru's evolution into a Demon Lord, it transformed into a Chaos Doll and moved to the Jura Tempest Federation with Ramiris. In Volume 16, Rimuru grants it a soul, awakening it into a higher sacred demon metal lifeform, the Chaos Metalloid.

This demon has a rare calm demeanor and is scholarly, with no interest in strength. It single-handedly takes on the role of advising Ramiris. Initially serving Ramiris under Rimuru's orders, during the banquet of the Demon Lords, it was somewhat coerced by Guy to swear loyalty only to Ramiris, officially becoming her subordinate. It was both the Dungeon Master and the leader of the Labyrinth's Ten Greats but resigned from the latter role, finding it troublesome, and handed it over to Gadra before the Eastern Empire's invasion of the labyrinth.

It possesses the unique skill "Contrarian" which automatically grants it opposite attributes, embodying both demonic and angelic traits. Through its awakening evolution, it acquired the ultimate ability "Deus Ex Machina," allowing it to freely transform into any metal shape.

Although it is a doll and originally genderless, in the anime version, it is shown entering a women's bath.