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
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 daemons. Other than that, she is just as good as Diablo in terms of political machinations, if not better.

Testarossa is capable of genuine friendship with other beings, having refused to take the payment of Blanche's soul even after completing her half of the contract; instead giving her a proper burial.

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 intimidated Framea the least; showing that even if she misunderstands the intentions of others, she doesn't hold it against them. Plus as a daemon, Testarossa is not used to the idea of having time off from her master's assigned tasks.

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 daemons, 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 Guardians 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.

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."