Testarossa

Testarossa (テスタロッサ), also known as Blanc (原初の白), is one of the Primordials that joined Tempest after Diablo recruited her, and the one who caused the infamous "Lake Shore Dyed Scarlet Incident". She is the military attache and the Minister of Foreign Affairs within Tempest as well as a leader of the Black Numbers along with Ultima and Carrera and is counted as a member among Rimuru's Twelve Guardian Lords.

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
Testarossa embodies the traits typically associated with a stereotypical noblewoman, evident in both her appearance and personality. Among the three Primordials recruited by Diablo, she displays the most mature demeanor but also exudes an air of haughtiness. While she carries herself with gentleness and elegance, she also harbors the inherent cruelty and battle hunger commonly found among daemons. In terms of political machinations, Testarossa's skills are on par with, if not superior to, Diablo's.

Her intolerance for subordinates speaking out of turn is apparent, as she is willing to resort to severe measures, such as cutting off Moss's ear, to enforce discipline. She also holds disdain for individuals who lack independent thinking or exhibit foolish behavior. On the other hand, Testarossa develops a sense of respect for those who demonstrate critical thinking, as shown by her admiration for Hinata's keen observation and foresight in understanding her master's plans.

Despite her formidable nature, Testarossa is capable of forming genuine friendships with others. For instance, after fulfilling her part of the contract with Blanche, she refuses to claim the payment of Blanche's soul and instead ensures a proper burial, signifying the depth of their bond.

Although equally perplexed as Ultima and Carrera regarding Rimuru's intention of granting them a day off for leisurely activities, Testarossa appears to intimidate Framea the least. This indicates that she does not hold misunderstandings against others and adapts to unfamiliar situations. Additionally, as a daemon, Testarossa is unaccustomed to the concept of having time off from her master's assigned tasks.

Background
Testarossa, like her primordial brethren, was born during the dawn of time before the creation of heaven and earth. She and the other primordials were demonic counterparts to the Seven Angels of Origin, split from the Great Holy Spirit of Darkness. They ruled Hell undisturbed for an eternity, with Rouge as their overlord. When Bleu and Vert were resurrected and became completely loyal to Rouge after their failed attempt to overthrow him, Testarossa, Violet, and Jaune made a pact to never engage in direct combat. Instead, they preferred to outsmart each other in games and vie for the opportunity to incarnate in the material world first.

In ancient times, Testarossa selected Silberia as her realm and forged a pact with its ruler of that era. This ancient pact declared that she would safeguard the land and foster its prosperity until an heir with the capacity to house her consciousness would the the perfect vessel arise. The distinctive red eyes of the Silberia royal family served as evidence of her blessing, granting them the ability to perceive beyond ordinary limits. Their bodies were dedicated to accumulating Magicules, harnessing a potent source of magical energy.

One day, Testarossa approached her ideal vessel, the princess of Silberia, then known as "Blanche Nam Silberia," As she stated in the pact, she would grant the girl's wish for the body to be hers. However, she was left puzzled when the girl's wish turned out to be a desire for friendship. Despite her confusion, she decided to embrace the opportunity and attached herself to the girl, taking on the role of guide and mentor, nurturing their relationship over the course of several years. However, nefarious individuals caused the Eastern Empire to invade the Kingdom of Silberia. Testarossa's powers were still developing, preventing her from stopping the invasion. In a desperate act, Blanche forcibly terminated their contract, allowing Testarossa to gain control of her body. Grief-stricken for the first time, Testarossa became enraged. She unleashed a forbidden spell, indiscriminately claiming the lives of both innocent and guilty, resulting in the infamous "Lake Shore Dyed Scarlet Incident."

After seeking vengeance against the main culprit, Testarossa cunningly pretended to be defeated by the Imperial Guardians of the capital. She abandoned her host body, severing ties with the physical world as a farewell gift to Blanche. To ensure her flesh would remain untouched, preserving its immortal beauty, Blanc cast a special seal, burying Blanche beneath the land.

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 and in short comic by the end Light Novel Volume 13 drawn by Taiki Kawakami himself.
 * Rimuru described the tea she made as "one of the best he had tasted."