Ultima

Ultima (ウルティマ), also known as Violet (原初の紫). She is one of the Primordials that joined Tempest after Diablo recruited them.

Appearance
Ultima takes the appearance of a cute and beautiful girl. She has middle length purple hair tied into a side ponytail, as well as purple fingernails. She wears a black military uniform with a skirt, with an armband on her left arm. She is shorter than both Carrera and Testarossa.

Personality
As a common trait for demons, she's a battle maniac. She usually acts cutesy, but is actually cunning, cruel and sadistic. She is also very egocentric and gets mad easily.

Chronology
She was recruited by Diablo who was looking for subordinates to help out with chores. At first, Rimuru thought she wasn't strong but Raphael quickly corrected him. She energetically introduced herself and pledged loyalty to Rimuru. She was so cute that Rimuru doubted that she as a demon at first.

The unnamed Ultima then gained a physical body by fusing together with an Emulated Soul and inhabiting one of the many homunculi bodies prepared by Rimuru. Her skeleton was slightly sculpted to retain her beauty, and gold was mixed in to turn the magisteel into Orichalcum. After she gained the body, Rimuru named her along with her two servants and 200 soldiers. The 2 servants were named Veyron and Zonda. Ultima and Veyron evolved into Demon Peer while Zonda has his limit as an Arch Demon released.

She was then assigned to be Chief Prosecutor of the Public Prosecution Office in Tempest. She accepted the job happily and was looking forward to it.

Rimuru Tempest
She was doubtful of Rimuru and wanted to kill him, but after he named her Ultima and gave her a body, she became extremely loyal.

Carrera
She's constantly at odds with Carrera. In the Underworld, they were always competing and battling with each other. Now they are competing for Rimuru's attention, while bickering with each other on daily basis. Their daily fights even become a subject of betting.

Testarossa
In the Underworld, they were always competing and battling with each other. Now they are competing for Rimuru's attention.

Diablo
In the Underworld, they were always competing and battling with each other. Now they are competing for Rimuru's attention. She's often beaten up by Diablo together with Carrera for their bickering.

Trivia

 * She was named after the Ultima GTR supercar.
 * She was shown in The Ways of the Monster Nation spin-off manga in chapter 42.
 * She addresses herself as "boku（僕）", a pronoun that is more commonly used by males.