If you have been keeping up with That Time I Got Reincarnated as a Slime (Tensura), you already know that Rimuru Tempest has assembled one of the most terrifying military nations in anime history. Yet, out of all his elite subordinates—the Twelve Patrons—one specific name sends absolute psychological horror through the world: Diablo.
To casual onlookers, he is simply the fanatical, impeccably dressed butler who would gladly erase a kingdom from the map because Rimuru ran out of matching teacups. But beneath that pristine silk suit lies a historical monster.
While figures like Benimaru hold the official military title of Supreme Commander, Diablo is universally feared as Rimuru’s strongest general. Let’s strip away the butler act and break down the ancient lore, his true power scale, and the jaw-dropping history of the Primordial Demons.
The Genesis Lore: Who Are the 7 Primordial Demons?
To comprehend just how broken Diablo is, you have to understand what he represents. In the Tensura universe, Primordial Demons (Gensho no Akuma) are not standard monsters born from stray magicules. They are primordial forces of reality co-created alongside the universe itself.
Eons ago, when the God Veldanava created light and shadow, the Seven Angels of Origin were born from the light. Simultaneously, from the deepest shadows of the Spiritual Realm, the Seven Primordial Demons emerged. They represent the absolute bloodline ancestors of all demonkind, categorized by a strict color spectrum:
- Rouge (Red) — Guy Crimson: The First True Demon Lord, currently ruling the Ice Continent.
- Noir (Black) — Diablo: Rimuru’s Second Secretary, personal guard, and strongest general.
- Blanc (White) — Testarossa: Jura-Tempest’s elite Chief Foreign Diplomat.
- Jaune (Yellow) — Carrera: Tempest’s Supreme Court Chief Judicial Officer.
- Violet (Purple) — Ultima: Tempest Military’s brutal Chief Prosecutor.
- Vert (Green) — Misery: Ancient subordinate vanguard serving under Guy Crimson.
- Bleu (Blue) — Rain: Ancient subordinate attendant also serving Guy Crimson.
For millions of years, these entities waged endless, cataclysmic wars in the Spiritual Realm purely to cure their eternal boredom. Because they were pure spiritual egos, they could not experience permanent death; if their spiritual cores were shattered, they would simply reform instantly.
The Unhinged Paradox of ‘Noir’: Why Diablo Capped His Own Power
Historically, Noir (Diablo) was the absolute thematic equal to Guy Crimson (Red). The two fought a countless number of times to permanent, world-shaking stalemates. However, when Guy chose to enter the physical world to accumulate raw power and evolve into the world’s very first True Demon Lord, Diablo chose a completely different path.
Diablo found the absolute pursuit of power uninteresting. To keep his skirmishes entertaining, he intentionally limited his own magicule capacity. He preferred challenging fights where he had to rely on flawless execution rather than overwhelming his opponents with raw energy.
The Ultimate Resurrect Glitch: Unlike the other Primordials who require decades, or sometimes centuries, to reconstruct their physical bodies if slain in the mortal realm, Diablo possesses an unpatchable cosmic cheat code. He has completely mastered instantaneous, unconditional resurrection. Even if you completely erase his soul, he wills himself back into existence a fraction of a second later with zero power loss.
The Mask of Fate: Why is Diablo Obsessed with a Slime?
Fans frequently laugh at Diablo’s unhinged, cult-like worship of Rimuru, but his devotion is built on profound metaphysical logic.
Long before Rimuru was even reincarnated, Diablo crossed paths in the physical world with Shizue Izawa, who was wearing the Anti-Magic Mask. When Diablo attacked her, the mask completely nullified his ancient power. He realized that this seemingly simple object contained an infinite, reality-bending temporal loop that defied the laws of the world.
Centuries later, when tracking the mask through his spirit scope, Diablo witnessed a low-tier Slime effortlessly swallow that exact mask, shatter the pre-determined fate of the world, and ascend into a True Demon Lord. To an ancient deity dying of absolute boredom, Rimuru was the ultimate answer.
When Rimuru finally cast a demon-summoning spell using the sacrificed bodies of 20,000 Falmuth soldiers, Diablo did not just answer casually—he systematically slaughtered every other high-tier demon in the underworld just to guarantee he would be the single one Rimuru selected.
Evolving Beyond the Rules: Diablo’s True Power Specs
When Rimuru bestowed the name “Diablo” onto Noir, it should have killed them both. Naming a high-tier monster requires immense magicule expenditure; naming an ancient Primordial Demon should have drained Rimuru’s life force instantly.
However, through the optimization of Rimuru’s internal evolutionary skill, Raphael (Great Sage), the naming succeeded seamlessly. By receiving a name, a physical body clone, and later a harvest of 100,000 souls during the Eastern Empire War, Diablo evolved from an Arch-Demon into a Demon Peer, and finally into a Devil Lord.
Diablo’s God-Tier Toolkit:
- Ultimate Skill – Azazel (Lord of Temptation): Grants him absolute authority over space, time, and cognitive perception. He can manifest an “Isolated Battlefield” where he controls the laws of local physics.
- Turn Real to Unreal: A terrifying reality-warping sub-skill. Diablo can impose a cognitive illusion of painful death upon a target’s mind. If the target’s consciousness succumbs to the illusion, their physical body immediately dies in the real world to match their mental state.
The Black Numbers: Rimuru’s Secret World-Ending Army
Diablo’s ultimate display of administrative efficiency came when he noticed that Rimuru’s core executive staff was becoming heavily overworked. His solution was beautifully terrifying: he returned to the demon underworld and forcibly recruited three more Primordials—Testarossa, Carrera, and Ultima—along with 700 of their highest-ranking demonic officers.
This elite attachment formed the Black Numbers, instantly making the Jura-Tempest Federation the most potent tactical military force on the planet.
When legendary global figures like Demon Lord Leon Cromwell and the Vampire Queen Luminus Valentine realized that Rimuru was utilizing world-ending, historic deities as simple workplace secretaries, international diplomats, and courtroom legal prosecutors, they genuinely believed Rimuru had completely lost his mind.
The Verdict: Is Diablo Unmatched in Tempest?
While Zegion possesses an intricate elemental type-advantage against demons, and Benimaru commands the strategic movements of the military, Diablo is undeniably Rimuru’s strongest general in terms of raw combat intellect, ancient combat experience, and complete immortality.
He is a multiversal cosmic threat hiding in plain sight behind a tailored suit and a silver tray—completely content with sweeping floors and brewing perfect tea for a slime, while possessing more than enough latent power to stand eye-to-eye with True Dragons.
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