Testarossa

Testarossa is a top-class demon of the race known as demons, initially an Upper Demon General (Arc Demon).

After being named by Rimuru Tempest, she evolves into a Demon Peer (Demon Lord–class) and later awakens as a Demon King of the "Majin" type.

She is one of the Seven Primordial Demons alongside Diablo and Guy Crimson.

Her epithet "Primordial White" reflects her silver-white hair and her status among the original demon pillars.

Testarossa is affiliated with the nation of the Jura Tempest Federation (Tempest).

She officially becomes one of Rimuru’s subordinates in the light novel volume 11 and receives his protection as her divine blessing.

Name: Testarossa

Alias / Epithet: Primordial White, Killer Lord (title among the Twelve Guardian Lords)

Species Titles Over Time:

Upper Demon General (Arc Demon)

Demon Peer (Demon Lord–class)

Majin (one of the Primordial Seven) – Demon King (Devil Lord)

Her name is derived from the Ferrari Testarossa supercar.

Within the story she is often referred to specifically as the "Primordial White" to distinguish her from other characters named Testarossa in other works.

Testarossa appears as a beautiful woman with white (silver) hair and striking red eyes.

Her refined and graceful appearance gives off the impression of a calm lady, which sharply contrasts with her battle-hungry and ruthless personality.

Her physical body in the material world is a special custom-made vessel provided by Rimuru Tempest.

Rimuru personally adjusted her appearance to be beautiful and even converted her skeletal structure into orichalcum (divine metal), making her body both elegant and extraordinarily durable.

Testarossa is intelligent, highly proud, and carries herself with elegance and absolute confidence.

However, she has a bad habit of looking down on others, seeing many beings as beneath her.

Despite her ladylike appearance, she is extremely aggressive and enjoys combat.

She can be cruel and merciless, as shown when she annihilated the Silberia Kingdom under the Eastern Empire, causing the infamous "Crimson-Stained Lakeside Incident."

She has a very willful side and will casually destroy even a loyal subordinate if they irritate her.

Because of this, her followers such as Moss and Shien are extremely careful around her and have survived long-term only by thoroughly understanding her temperament.

Among the Primordial Demons, she is considered the most proud.

Guy Crimson believed she was the kind of being who could never serve under anyone, so he was genuinely shocked when he learned she had chosen to serve Rimuru Tempest.

Even so, she has a surprisingly "sane" side similar to Guy Crimson.

She often becomes exasperated by Diablo’s battle-maniac perspective and is bewildered by Shion’s values, which even make Diablo pause.

In work-related matters she is extremely capable, calm, and precise.

She always acts after reading ahead of her master Rimuru’s intentions and is highly efficient in both diplomacy and administration.

She is also very skilled at brewing black tea, to the point of surpassing Shuna’s abilities.

Her fine attention to detail and social graces make her arguably the most suitable candidate for the role of Rimuru’s secretary.

Rimuru, however, refuses to make her his exclusive secretary because doing so would force him to assign either Shion or Diablo to frontline diplomatic positions.

Anticipating the chaos that would cause, he reluctantly keeps Testarossa as a diplomatic officer instead.

Testarossa is recognized as one of the most dangerous Primordial Demons, on par with Diablo in terms of threat level.

Her specialty is extremely precise magicule (magical energy) control and refined combat technique.

Because of her mastery of energy control and technique, she can fight on equal footing with opponents whose total energy is ten times her own.

Among the Primordials, she was already feared for her combat skill even before her later evolutions.

Her listed energy points total is approximately 3,333,124.

She is one of the Twelve Guardian Lords under Rimuru Tempest and holds the title of Killer Lord, indicating her dominion over slaughter on the battlefield.

Magic and Skills

Testarossa uses dark magic and elemental magic as her primary spell systems.

She is especially associated with destructive, death-oriented magic that targets both body and soul.

She later acquires the ultimate ability "King of the Underworld (Berial)", a power governing life and death.

Compared to Luminous Valentine’s "King of Lust (Asmodeus)"—which also handles life and death—Testarossa’s ability is more strongly aligned with death.

Her ultimate ability includes the following aspects and effects:

Thought Acceleration: Enables ultra-fast thinking and analysis.

Universal Perception: Allows her to perceive all phenomena within a chosen range.

Demon Lord’s Haki: A dominating aura that exerts pressure and control over others.

Space-Time Manipulation: She can interfere with space and time, enhancing both mobility and defensive options.

Multidimensional Barrier: Enables the construction of layered multidimensional defenses.

Omniscience-like Perception of All Things: A broad understanding and sensing of all phenomena.

Life Control: Direct control over life forces, including the ability to grant or retract life in certain conditions.

Afterlife World: Authority over a death-related domain or afterworld, allowing her to influence souls beyond death.

Resistances

Testarossa is highly resistant or outright immune to most forms of attack.

Her listed resistances include:

Immunity to physical attacks

Immunity to status abnormalities

Immunity to mental attacks

Immunity to natural environmental influences

High resistance to holy and demonic type attacks

These resistances make her extremely difficult to injure or manipulate, especially by conventional magic or physical means.

Death Blessing (Death Streak)

"Death Blessing" (also rendered as Death Streak) is a forbidden nuclear-class magic that Testarossa uses during the war with the Eastern Empire.

It uses a Black Flame Core (Abyss Core) as its catalyst.

She crushes a Black Flame Core in her hand, releasing a "black light" that radiates outward.

This light forcibly rewrites the genetic structure of any living beings within range, causing them to die without exception.

This spell is extremely dangerous not only because it destroys the body but also because it annihilates the target’s soul.

No human killed by this magic has ever revived as a monster or anything else, unlike some other death events in the series.

There is a theoretical possibility that, under special conditions, a human struck by this power could reincarnate as a monster.

However, the probability is so low that it is practically nonexistent, and no successful case has been recorded.

According to Testarossa, this is the same type of magic that Guy Crimson used when becoming a Demon Lord.

This makes Death Blessing a historically significant spell within the world’s lore.

Ultimate Ability: King of the Underworld (Berial)

Testarossa acquires "King of the Underworld (Berial)" as a result of her growth, particularly during the war with the Eastern Empire and after facing intense battles such as the one involving Velgrynd.

Her discussions with Diablo and her introspection about her own inner nature push her further toward the domain of death.

"King of the Underworld" governs both life and death but is biased toward death, making her one of the most lethal beings in existence.

This ability integrates her precision magic control with divine-level authority over living souls and the afterlife.

Testarossa belongs to the Jura Tempest Federation under Rimuru Tempest.

She receives Rimuru’s blessing and later a portion of his soul, which allows her to awaken to Demon King–class as a Majin-type Demon King.

She is formally appointed as one of the Twelve Guardian Lords, elite guardians serving Rimuru.

Her individual title within this group is Killer Lord, reflecting her role in mass combat and extermination.

In addition to combat duties, she serves as a diplomatic military officer, acting as Rimuru’s plenipotentiary representative.

She combines political acumen, negotiation skills, and overwhelming force to secure Tempest’s position on the world stage.

Her voice in animated adaptations such as "Coleus’ Dream" and "The Great Clash of Demon Lord and Dragon’s Founding Chronicle" is provided by voice actress Yumi Uchiyama.

These adaptations help further highlight her character and increase her popularity.

Early History as Primordial White

Before the main story begins, Testarossa rules over regions to the east, near the territory of the Eastern Empire.

She is feared as the "White Demon" who reigns over that area.

For many years, she constantly clashed with two other Primordials:

The "Purple" (later known as Ultima)

The "Yellow" (later known as Carrera)

The three of them engaged in endless power struggles, shaping the power balance in the Eastern regions.

Testarossa’s presence alone was enough to keep many forces in check.

During this era, she caused the notorious Crimson-Stained Lakeside Incident, in which she wiped out the Silberia Kingdom, a vassal state of the Eastern Empire.

The incident left a lake and its surroundings dyed red, symbolizing her ruthlessness and cementing her terrifying reputation.

Encounter with Diablo and Rimuru Tempest

At some point, Diablo approaches the three Primordials—Testarossa, Ultima, and Carrera—to recruit subordinates for Rimuru Tempest.

Where Ultima and Carrera are taken by force after violent clashes with Diablo, Testarossa agrees far more smoothly.

Unlike the others, she accepts Diablo’s invitation partly out of curiosity.

She is intrigued by the idea of the master that even Diablo, a fellow Primordial, values so highly.

Initially, she only intends to temporarily lend her strength to Rimuru.

Her plan is to evaluate him and even considers killing him if she finds him uninteresting or unworthy.

However, when she finally meets Rimuru Tempest, she immediately understands why Diablo holds him in such high regard.

Instead of disappointment, she finds herself impressed and deeply fascinated by him.

As a result, she voluntarily declares her loyalty and becomes a true subordinate of Rimuru.

This decision later shocks other powerful beings, especially Guy Crimson, who never imagined Testarossa would serve anyone.

Becoming Rimuru’s Subordinate

After pledging her loyalty, Testarossa receives a name and a special body from Rimuru.

Rimuru designs her vessel to be aesthetically pleasing and reinforces it with orichalcum bones, making it a unique, high-grade physical form.

Upon being named, she evolves into a Demon Peer, effectively a Demon Lord–class being.

This evolution increases her energy and pushes her closer to the top tier of combatants in the world.

Rimuru then appoints her as his diplomatic military officer, granting her full authority to act as his representative in foreign affairs.

She is dispatched to the Council of the Western Nations as his plenipotentiary envoy.

Diplomatic Activities in the West

At the Western Nations Council, Testarossa demonstrates both her cunning and restraint.

She cleverly resolves a conspiracy involving Guy Crimson’s subordinate without directly staining her own hands.

Through this maneuver, she demonstrates Tempest’s political strength and reliability.

Her handling of the crisis helps solidify the Jura Tempest Federation’s position among the Western countries.

Testarossa herself believes that, in the end, everything unfolded "in the palm of Rimuru’s hand."

She attributes the success largely to Rimuru’s foresight, seeing herself as the executor of his design.

She also takes command of the Western Deployment Army, composed of support troops gathered from various nations by the Western Council.

As its corps commander, she coordinates military forces under Tempest’s banner.

War with the Eastern Empire

During the war with the Eastern Empire, Testarossa has ample opportunities to act, due in part to her deep connections with the East.

Her history with the Empire and the earlier destruction of the Silberia Kingdom tie her emotionally to the conflict.

She fights on the front lines and deploys her devastating magic, including Death Blessing.

Her actions on the battlefield contribute significantly to Tempest’s military victories.

Through these intense battles and the experiences she gains, including information shared by Diablo and clashes with high-level opponents like Velgrynd, she is forced to confront her own inner nature.

By embracing her affinity with death and refining her understanding of life and death, she attains the ultimate ability King of the Underworld (Berial).

Later, in volume 15, Rimuru grants her a portion of his own soul.

This soul transfer allows her to undergo an awakened evolution, rising to the rank of a Majin-type Demon King (Devil Lord).

Post-War Role and the Eastern Empire

After the war against the Eastern Empire, Testarossa’s role shifts to stabilizing the new political order.

Honjou Masayuki ascends as the new emperor of the former Eastern Empire.

Because Testarossa has deep ties with the Eastern regions from her prior life as a ruling demon, she is a natural choice to handle diplomacy there.

She leaves the management of the Western Council duties in the hands of Shien.

Testarossa then goes to the Empire to serve as a diplomatic officer under Honjou Masayuki’s reign.

This puts her at the core of Tempest’s relationship with the newly transformed Empire and extends her influence across both East and West.

Rimuru Tempest

Rimuru Tempest is Testarossa’s master and the person she chooses to serve wholeheartedly.

She is genuinely impressed by his power, vision, and charisma, and her loyalty is deep and sincere.

She sees herself as an instrument of Rimuru’s will and often acts after carefully considering what would most benefit him.

Even when she independently resolves complex situations, she tends to credit Rimuru’s planning rather than taking all the glory.

Her admiration for Rimuru borders on devotion, aligning her with other fanatically loyal subordinates like Diablo.

However, she retains a composed, aristocratic demeanor rather than openly obsessive behavior.

Diablo

Diablo is a fellow Primordial Demon and the one who originally invited Testarossa to Rimuru’s camp.

They are roughly equal in terms of threat, and their relationship is a mix of rivalry, mutual respect, and shared pride.

Testarossa is often exasperated by Diablo’s extreme battle-hungry worldview.

Despite that, she recognizes his capabilities and treats him as someone of the same "class" among the Primordials.

Diablo’s stories about Rimuru influence Testarossa’s expectations before she meets him.

After joining, they both serve as top-tier enforcers and administrators under Rimuru.

Guy Crimson

Guy Crimson, known as the Primordial Red and the oldest Demon Lord, has known Testarossa for a long time.

He always considered her too proud to serve anyone, regarding her as someone who would never accept a master.

When he learns that Testarossa has become a subordinate to Rimuru Tempest, he is genuinely stunned.

This reaction highlights just how surprising and significant her decision to serve Rimuru is within the primordial community.

Ultima and Carrera

Ultima (formerly the Primordial Purple) and Carrera (formerly the Primordial Yellow) are fellow Primordials who long fought against Testarossa in the East.

For many years, the three engaged in continual territorial clashes and power struggles.

Under Rimuru, all three now serve the same master.

Where Ultima and Carrera were dragged in after violent battles with Diablo, Testarossa joined more voluntarily thanks to her curiosity.

Even so, their long history of rivalry influences their dynamics.

They remain tremendously dangerous in their own right and form a deadly trio among Rimuru’s forces.

Shion and Shuna

Shion is Rimuru’s battle-obsessed secretary, while Shuna oversees domestic affairs and also serves him closely.

Testarossa compares unfavorably to neither: in fact, she is arguably the most suitable secretary of the three.

Shion and Diablo often quarrel over the position of Rimuru’s secretary, causing chaos around him.

Testarossa, by contrast, is calm, efficient, and attentive, clearly fitting the role better on paper.

However, Rimuru avoids making her his main secretary to prevent having to deploy Shion or Diablo as diplomatic officers, which could destabilize foreign affairs.

Testarossa accepts this and excels in the diplomatic role instead.

Testarossa also surpasses Shuna in brewing black tea, revealing a refined domestic skill set.

Her ability to combine combat strength, diplomacy, and hospitality makes her stand out in Rimuru’s inner circle.

Moss and Shien

Moss and Shien are Testarossa’s subordinates, acting as her long-term attendants and aides.

They know her temperament extremely well, especially her tendency to eradicate even loyal followers if they annoy her.

Because of this, they behave with constant caution and thorough consideration in her presence.

Their survival and continuing service testify both to their competence and their ability to navigate Testarossa’s whims.

In the original web novel version, Testarossa appears but has red hair like Guy Crimson.

At the time, the concept of the Primordial Demons and their color-coded identities had not been fully established, leading to this overlap.

In the light novel version, her design was revised to make her the Primordial White, giving her white hair.

This change differentiates her visually and symbolically from Guy Crimson and better fits the Seven Primordials’ color scheme.

The light novel significantly increases her role compared to the web novel.

She is heavily featured due to her status as Rimuru’s plenipotentiary and as a key player in diplomatic and military events.

Her past, including incidents like the Crimson-Stained Lakeside Incident and her rule in the East, is explored in dedicated short stories.

Among the Primordial Demons (aside from Diablo), she is arguably the most heavily spotlighted and "favored" by the narrative.

In later media, such as the anime and related projects, Ultima also receives considerable focus.

Because of this, Testarossa no longer monopolizes attention among the Primordials, but she remains one of the franchise’s standout characters.

For clarification in fanworks and databases, it is often recommended to tag her as "Testarossa (That Time I Got Reincarnated as a Slime)" rather than just "Testarossa."

This avoids confusion with characters of the same name from other works.