Testarossa

Testarossa (テスタロッサ), also known as Blanc (原初の白). She is one of the Primordials that joined Tempest after Diablo recruited them, and the one who caused the infamous "Lake Shore Dyed Scarlet Incident".

Appearance
She is an alluring lady with waist-long white hair and crimson red eyes. She usually wears a black military uniform with baggy pants, while her formal attire is a teal-colored dress. Out of the 3 Primordials recruited by Diablo, she is the tallest.

Personality
As her appearance suggests, Testarossa has the personality of a stereotypical noblewoman. Out of the three Primodials recruited by Diablo, she has the most "mature" personality, but is also the most haughty among them. She is gentle and elegant in mannerisms, but also has the cruelty and battle hunger common among demons. Other than that, she is just as good as Diablo in terms of political machinations, if not better.

While equally clueless as Ultima and Carrera as to what Rimuru intended with giving her a day off to enjoy some leisurely activities, Testarossa actually intimated Framea the least; showing that even if she misunderstands the intentions of others, she doesn't hold it against them.

Background
Silberia had been her domain since time immemorial. And according to the ancient pact formed with the ruler of the land, she adjusted for dozens of centuries before a vessel of flesh used to accommodate her mind would be born. Until the birth of her ideal vessel, she would protect the land. This was the content of the pact. And the special physique of the royal family was a testament to it. The red eyes of the Silberia royal family were her blessing. Early rulers of Silberia formed a covenant with the master of many demons, Primordial Blanc. Its content being to facilitate the coming of Blanc to this realm, and in return, she would be the guardian of the kingdom of Silberia. Testament to the pact were the 'Crimson Eyes' that could see through anything, a power only possessed by the king's lineage. With the purpose of inheriting a cursed bloodline and amassing magicule throughout generations. And then, when the heir with the ideal flesh for the Primordial appears, it shall possess it and come forth to this world once more.

After her pact with the princess "Blanche Nam Silberia" was completed she pretended to be defeated by the Imperial Royal knights of the capital. She left her host body and cut ties with the physical world as her parting gift for Blanche. In order for no one to ever touch her flesh and let it rest in immortal beauty, Blanc casted a special seal to bury Blanche beneath this land.

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 was excited to meet Rimuru and hoped he would accept her. After changing locations the unnamed Testarossa gained a physical body by fusing together with an Emulated Soul and inhabiting one of the many bodies in the growth capsules prepared by Rimuru. Fitting for their status, all 3 Primordials' skeleton has gold mixed in and turned into Orichalcum, further improving the performance. After she gained the body, Rimuru named her along with 2 of her servants and 200 soldiers. The 2 servants were named Cien and Moss. Testarossa and Moss evolved into Demon peers from being named while Cien evolved into an Arch Demon.

A bit later Testarossa was assigned with being the Military Attaché, a representative for The Council of the West. Testarossa accepted it with a gentle smile promising there would be no problems.

While Rimuru was in Ruberios a Western States Council meeting took place. The meeting was in a huge crisis due to the main defense force of the Sidel border region disappearing. The demons from Guy's territory could easily run down Ingracia like this. The emergency force to defend the country would be handled by Testarossa which was an unanonimous decision but there were still complaints. Testarossa calmed everyone and asked Moss to report the situation to everyone in the meeting. After this the council members begun arguing which Testarossa listened to quietly. During this she eavesdropped on Johann Rosteia, the duke of the Rosteia Kingdom, who was using Magic Communication to give orders to disrupt the barrier around the city. She confronted Johann but was interrupted by the Apostles of Vert who summoned the Green Primordial, Misery. After Misery arrived she confronted Testarossa but in the end retreated and said she would fight Testarossa the next time they meet. With this everyone in the council learned Testarossa's true identity as the White Primordial but she also conquered the Western States Council and became highly influential in it.

Relationships
Diablo: In the Underworld, they didn't have a great relationship. Now Testarossa is grateful for Diablo introducing her to Rimuru; They seem to get along with each other since leaving the underworld and being summoned by Rimuru.

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

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

Rimuru Tempest: She was brought alongside the two other Primordial Demons and all their main underlings to Tempest by Diablo as she was interested in seeing the master Diablo served. Finding Rimuru to be as interesting as Diablo advertised after Carrera's full-power intimidation didn't even make Rimuru flinch, she joined Tempest and was given a physical body and the name Testarossa. She evolved into a Demon Peer alongside Carrera and Ultima. Testarossa serves in the Black Corp under Diablo but is also Tempest's Military Attaché, regularly taking post as the Ambassador to the Council of The West. She often competes with Ultima and Carrera for his attention.

Blanche Nam Ul Silberia: She is Testarossa's first friend, they got along well and Testarossa deeply cared about her. After the death of Blanche, she refused to consume her soul and decided to bury her body in the land of Silberia, along with the souls of others who did not break the pact.

Trivia

 * She was named after the Ferrari Testarossa supercar.
 * She briefly appears in The Ways of the Monster Nation spin-off manga in chapter 42.
 * Rimuru described the tea she made as "one of the best he had tasted".