- Asskicking Equals Authority: Half of the reason they follow Rimuru so loyally is the fact he is one of the strongest beings in the world, with him using that power to either protect them from harm by other strong people, or defeat them and push them into submission after they tried to harm him.
- Because You Were Nice to Me: The other half of why they're loyal to Rimuru is because of how much of a Benevolent Boss he is, equally treating every citizen with kindness, no matter what race they are or even if they tried to harm him and his allies before.
- True Companions: It's not to the same extent as their loyalty to Rimuru, with the relationships between citizens being anywhere from as close as family to as strained as rivals, but every single citizen of Tempest has a strong bond with the rest of it, being able to count themselves as having the others' backs and vice-versa.
- Undying Loyalty: One consistent trait among every citizen in Tempest is that they maintain complee and total loyalty to Rimuru, with them considering him the greatest being in the world and willing to do anything that he desires of them.
A king and ruler of the Armed Nation of Dwargon, the main dwarven kingdom around.
- Authority Equals Asskicking: The ruler of his nation and the strongest member of it.
- Badass Baritone: In the English dub, he's given a very deep voice by Randy E. Aguebor (which, by the way, is his normal speaking voice).
- Disappointed in You: Tells Vesta this after the exile of Rimuru, Kaijin and his brothers from the kingdom despite knowing of their innocence, having known from the beginning about even Kaijin's innocence in the failure of Vesta's Magisoldier Project. He spent years waiting and hoping that Vesta would come forth and admit the truth, but Vesta's refusal and the sham trial brought his patience to an end.
- Flash Step: A skilled swordmaster, way quicker than anyone would expect from a dwarf.
- Just Between You and Me: Played for drama. While Gazel had to make Kaijin appear as the aggressor of the ordeal, he privately let Vesta knew that he was fully aware of everything that was going on.
- Killing Intent: Strong enough to paralyze opponents, despite not actually being violent by nature. Being able to focus his will to such extent seems to come with being a king.
- Our Dwarves Are All the Same: Subverted similarly to Vesta Gazel too could be easily mistaken for a human, being much taller and slimmer than an average dwarf.
- Reasonable Authority Figure: Although he's presented as a legitimate badass and an intimidating figure, he's also quite reasonable and able to see what's actually going on. He knows full well that he's presiding over a sham trial over Kaijin, Rimuru and the others orchestrated by Vesta, and he implies that if Kaijin hadn't already decided to turn his talents over to Rimuru and rejoined the military, he would have dropped the charges completely. Instead, he changes the sentence from years of hard labor in the mines to exile, thus allowing Kaijin and his fellows to leave with Rimuru without issue.
Dwarven aristocrat and scientist who works as a Gazel's minister, which drives him into conflict with Kaijin. After embarrassing himself before his king and being exiled for that, he reconsider his ways and becomes Rimuru's chief scientific advisor.
- Aristocrats Are Evil: Or at least excessfully prideful and inconsiderate. He gets better.
- The Atoner: Becomes this after his banishment.
- Break the Haughty: He was nothing but arrogant and condescending, but after Gazel revealed that he knew everything he was doing and was disappointed that he refused to come clean, he became a sobbing mess. By the time Rimuru meets him again after Gazel drops him off in Tempest to work for him, he spent over an hour apologizing to him.
- Defeat Means Friendship: After being outsmarted by Rimuru, he decides that it's better to work with him than against him.
- Driven by Envy: His jealousy of Kaijin for being a commoner who managed to become his superior is what lead him to antagonize the dwarf and pin the blame for his own failings on him.
- Gentleman and a Scholar: A high-ranked aristocrat with a passion For Science!, which makes him conflicted at times, though he gets better.
- HeelFace Turn: After he is shamed by Rimuru and banished from the Dwarf king's court, he moves to Tempest and becomes a scientist and adviser to Rimuru.
- Mad Scientist: Has a heavy vibe before his HeelFace Turn, fueled by his ambition and pressures of a government position. When he resolves his internal conflicts, he becomes a pretty standard Gentleman and a Scholar.
- My God, What Have I Done?: When Gazel reveals that Rimuru was the creator of the extremely pure healing potion, and that his actions may very well have terminated what could have been a powerful alliance with the slime, Vesta is beside himself with regret.
- My Greatest Second Chance: Considers his service as a researcher for Rimuru to be this, as the alliance between Tempest and Dwargon means any successes he has will benefit both nations, simultaneously atoning for his past misdeeds and continuing to serve king Dwargo's interests.
- Our Dwarves Are All the Same: Interestingly, he's actually pretty tall and slim compared to many other dwarves, to the point he could easily be mistaken for a human.
- The Rival: To Kaijin, which leads to his Driven by Envy Start of Darkness.
- Well-Intentioned Extremist: Jerkass aside, he does want to be a helpful minister to Gazel, and his realization that he allowed his own failings to ruin what could have been a powerful partnership with Rimuru causes him to break down in tears.
A dwarven blacksmith that befriends Rimuru after helping cure some of his friends. He joins Rimuru after being exiled thanks to Vesta.
- Birds of a Feather: He and Kurobee become friends soon enough because of their shared passion for blacksmithing.
- The Blacksmith: An incredibly skilled one at that, being charged with forging the weapons for the dwarven military.
- The Exile: Leaves Dwargon to join Tempest after being exiled.
- Retired Badass: He was once the captain of one of the seven orders of holy knights in the kingdom, though he was forced to retire due to Vesta's actions.
- The Rival: To Vesta both in military and as an artisan. In fact, being passed over for promotion in favor of Kaijin was Vesta's Start of Darkness.
The captain of the Dwarven Kingdom Guard, who briefly detained Rimuru and Gobta after an unfortunate incident outside the Kingdom's gate.
- I Owe You My Life: More like "I owe you my friends lives". After Rimuru made a large amount of high-quality recovery medicine to help the survivors of monsters in the mines, whatever suspicions Kaido had about him were wiped away.
- Not What It Looks Like: He and other guardsmen rushed up to a commotion outside the gates and discovered a group of unconscious and panicking people centered around two monsters. This was because a large group of people had started harassing and attacking Rimuru and Gobta, and the former used an intimidation power to scare them off.
- The Power of Trust: Accepting the above-mentioned recovery medicine from a pair of monsters (one of who had escaped both the bars he was behind and the barrel he'd been stuck in), was a leap of faith that made things better for everyone, in the end.
- Reasonable Authority Figure: Acknowledged that Rimuru's story about self-defense matched up with the witnesses' testimony, and seemed ready to give him the benefit of the doubt, even before Rimuru made a large amount of recovery medicine to help a number of injured dwarves.
- Spell My Name with an "S": Kaito, Katou
- Fighter, Mage, Thief: Cabal is the fighter, Ellen is the mage and Gido is the thief
A regional Guildmaster for the kingdom, he's a local administrator of the powerful Adventurers' Guild, and a childhood friend of the nation's Prime Minister, making him quite an influential person in the region. Befriends Rimuru rather fast, and is his frequent guest and co-conspirator.
- Author Avatar: Being named the same as the author's pen name, has raised a whole lot of suspicions.
- The Chessmaster: Is heads-deep in the politics between his kingdom, the Guild and the whole host of plots around Tempest meteoric rise.
- Da Chief: As Guild is often relied on to provide policing in urban areas, with some adventurers in effect becoming a career police officers, he's that as well.
An adventurer with the classification of "Fighter" under Fuze's command, he leads a small party of adventurers on journeys that more than not end up crossing paths with Rimuru.
- Deflector Shields: Can cast a barrier spell to protect himself and others. It comes in handy when it lessens the explosion of a Salamander from "fatal" to "badly wounding."
- Heroes Prefer Swords: Carries a broadsword on his back.
- Leeroy Jenkins: He seems to have a habit of causing the party trouble, such as when he aggravates a Giant Ants' nest.
An adventurer with the classification of "Thief" under Fuze's command, he serves as an exasperated voice of reason to his two companions.
An adventurer with the classification of "Mage" under Fuze's command, she serves as the moral center of sorts for her trio of comrades.
- Call to Adventure: Why she became an adventurer. She wanted freedom away from being a noble.
- An Ice Person: Can cast the spell Icicle Lance. Rimuru copies and improves it to make Icicle Shotgun.
- Magic Staff: A wooden staff tipped with a giant blue crystal ball, through which she casts her magic.
- Really Royalty Reveal: She's actually Elyune, a noble from the Sorcery Dynasty of Sarion.
The head of the Adventurers' Guild and yet another Japanese person transferred into this world. He has some connection to Shizue and thus to Rimuru, and later becomes a major antagonist.
- Big Bad: Eventually, due to the very complicated (and contrived) turn of events.
- The Chessmaster: Yuuki was a genius from his kid years and excels in scheming and manipulations.
- It Amused Me: From his earliest days he was bored to death with an ordinary life, and anything he does is entirely for his own amusement.
- Keystone Superpower:
- Information King-Akashic Records allows him to use almost every ability in the series.
- Primitive Magic reflects the user's will and produces the phenomena they want .
- Older Than They Look: He's in his late twenties, but for some reason, his physical appearance has locked on his teenage form.
- Otaku: And a pretty hardcore at that. Rimuru was able to get on his good graces just by providing the latest issues of some popular manga series that he missed in this world.
- Pop-Cultured Badass: On account of having been a hardcore nerd in his past life, Yuuki is well-versed in numerous video-games and manga. He's also an extremely powerful Hero capable of wiping the floor with people who upset him.
- Teen Genius: Outwardly. He's really in his late twenties.
- Terrorists Without a Cause: There's basically no reason for Yuuki adopting his outlook except some very vague Freudian Excuse and sheer boredom.
- Villain with Good Publicity: Early on, he went to great lengths to concoct a kind and reasonable persona doing a lot of good deeds to increase his influence. In actual fact, however, Yuuki's a twisted psychopath reveling in the destruction he brings.
The Kingdom of Farmus
- An Arm and a Leg: Rimuru slices off his arm when he foolishly points at the very same guy who wiped out 20,000 of his troops single-handed and said "on your knees, monster! You are in the presence of King Edmilas of Farmus!"
- Beard of Evil: Full beard, greedy, cowardly, and wicked sot who attacked Tempest, expecting an easy victory, riches, and land to exploit.
- Blatant Lies: When Rimuru demands to hear the King's side of the story, King Farmus tries to say the entire army are his personal body-guards, he was seeking peaceful relations, and the attack on Tempest was a "misunderstanding," with the criminals in his employ having duped him as well. Rimuru listens to the very end before stating that he has no shred of credibility and taking him as a P.O.W. so that his country pays ransom for his aggression.
- Break the Haughty: Makes tent at one of the four magic barrier crystals debuffing the "monsters" in Tempest expecting an easy victory and gloating how he's going to rake in the spoils. When his invading army is wiped out and all the barrier crystal stations are totally annihilated, he begins panicking and trying to sneak out the back of the tent, until everything goes quiet. He briefly recovers when Rimuru shows up, and he thinks he can browbeat the leader of Tempest due to the "Nice Guy" reputation Rimuru's built up, only to break down completely at losing an arm and Rimuru stating "if you think I'm a nice guy, you are sorely mistaken."
- Dirty Coward: Tries to flee the instant he realizes he's on the losing end of the fight with Tempest, leaving all his allies behind. He doesn't get anywhere.
- Hope Spot: Repeatedly. In the dungeons under Tempest, as he's surrounded by the Body Horror that was his advisers who recommended the ill-advised attack on Tempest, he repeatedly shouts that he's the king of Farmus and begs for aid. Two of Tempest's citizens visit him while his remaining arm is chained to the wall.
- He is first met by Shion. She greets him politely, tells him he's not going to be killed, tells him she forgives him for her death at the hands of his troops, and tells him that Rimiru likes humans, of which he is one. Then she reveals that she will never forgive that his attack forced Rimuru to kill humans by the legion, and beats the ever loving shit out of him, stating that even if she had permission to kill him, shredding him to pieces 10,000 times would not be enough to end her rampage.
- He is later visited by Rimuru, not wearing his mask. King Edmalis mistakes the androgynous Rimiru for a servant girl and tries to bribe his way out. Rimiru asks him if he's forgotten his voice and slaps the mask on, then advises the king that freedom is not forthcoming, and that the burden for the attack on Tempest will be something he'll have to live with the rest of his life, leaving King Edmalis to wallow in his despair and terror.
- Implausible Deniability: Tries to claim he knew nothing about the aggression of his troops and cowardly sneak attack of his Black Ops team. Rimuru didn't buy a word of it.
- Stunned Silence: After Rimuru chops his arm off in annoyance, he spends several beat panels wordlessly staring at the stump before he collapses to the ground in agony.
- Villains Want Mercy: Begged for his life the moment a pissed off Rimuru gives him the chance to speak.
- Wrong Assumption: He presumed Rimuru, who had just slain over 20,000 of his soldiers, right in his face, would be a "soft, easy mark, lousy at diplomacy" based on out-dated intelligence reports. So he commands Rimuru to kneel, stating that he's someone Rimuru should not mess with. He loses an arm to Rimuru's wrath, just to show him how wrong he is.
- Asshole Victim: Given just how much of a complete scumbag he was, not a single hint of concern or care is given to him being transformed into a horrifying mass of flesh by Shion. The story doesn't even bother lingering on it, only leaving it as a passing footnote.
- Ain't Too Proud to Beg: Shamelessly begged for his life to a pissed off Rimuru. He lost what little respect Rimuru had for him as a result.
- Bald of Evil: Not a single hair on his head, and a coward who spurred the kingdom of Farmus into a genocidal attack on Tempest.
- Body Horror: While he survives a bit longer than Razen, he's eventually forced through the same experience of being turned into a horrifying mass of still-living flesh, bones and organs thanks to Shion.
- Dirty Coward: The moment Tempest retaliated, he and King Edmalis cowered in the king's tent, planning to flee, abandoning their troops and allies.
- It's All About Me: The only life he cares about is his own, even willing to offer up King Edmalis to spare himself.
- Villains Want Mercy: Facing off against a pissed Rimuru, and he doesn't hesitate to drop to his knees, bowing his head to the ground, begging for his life.
- The Arch Mage: He has mastered many powerful and varied spells and types of magic, including summons.
- Asshole Victim: No tears were shed when the Demon later named "Diablo" beats the tar out of him as he foolishly resists being taken into custody. Even less of a damn was given for what happened to him at Shion's hands.
- At Least I Admit It: When he's lecturing Shougo Taguchi at the guy's last moments, he admits that the kingdom of Farmus, and the summoners who summoned and enslaved him, as well as Razen himself, are not good people, but Shougo is no good person either."Needless to say, we are not good people, but neither are you."
- Body Horror: When he shows up again following his capture by Rimuru, Shion has subjected him to Cold-Blooded Torture using her "Chef" skill, turning him into a writhing mass of flesh, bones and organs that is almost impossible to tell ever used to be a human being. He's also still alive in this form, unable to utter a sound while his body twitches in agony.
- Faking the Dead: He pretends that Rimuru's attack kills him, waiting for an opportunity to try and escape. This prompts Rimuru to summon demons to hunt him down.
- Fatal Flaw: Arrogance. He presumes he's always better than everyone else in the room. When he tries to fight off a "Demon of the Primal Colors," he realizes this is wrong a bit too late, and suffers for it.
- Grand Theft Me: He steals Shougo's body, after making Shougo brain-dead, on-screen.
- Kick the Son of a Bitch: Using a magic spell to make Shougo brain-dead to then steal his body gave the latter a Karmic Death.
- Know When to Fold 'Em: He's usually well-versed as to when he's outmatched in combat, and when this happens, he always prioritizes his escape, but never, ever surrenders. The last part does eventually catch up to him when he tries to sneak away, fails, and then attempts to resist being taken into custody.
- So Long, Suckers!: If he has to withdraw publicly, he makes a show of it. This is justified by the fact that anyone foolish or naive enough to attempt pursuit is usually going to run face-first into a booby-trap.
- Bling of War: Wears shiny metal armor.
- Boom Head Shot: On the wrong end when Rimuru is laying waste to the armies of Farmus. One of Rimuru's beams of light pierces his brain, killing him instantly.
- Card-Carrying Villain: Doesn't bother to hide how despicable he is. He even laments the deaths of Kyouya and Kirara, because they died in a way that kept him from stealing their skills.
- Jumped at the Call: When he was summoned by the magicians of Farmus, he was overjoyed, and didn't need to be magically enslaved.
- Power Parasite: He steals the special skills of any subordinate who dies before him, but there's a limit to how many skills he can steal this way.
- You Have Outlived Your Usefulness: He's fond of killing his underlings when they're no longer useful, so he can steal their skills.
Common to all:
- Asshole Victim: Despite their Freudian Excuse, their actions are so vile, nobody sheds a tear at their deaths, not even each other, aside from moments where the death of one inconveniences the others.
- Freudian Excuse: They are summoned without warning, or consent, enslaved by a magical curse, and forced to fight in an alien war with their lives on the line. This would grind on the sanity of anyone, but it's implied that they weren't good people to begin with.
- Kidnapped by the Call: They were summoned against their will and without warning to the world of the story.
- Lack of Empathy: They don't care about anyone else, not even each other, unless it suits their needs.
- Sadist: They love seeing others suffer. If they're the ones suffering, on the other hand...
- Smug Snake: They love to flout their self-perceived superiority over others, but when they're on the losing end, they're quick to have a breakdown.
- Trapped in Another World: Like all the "wanderers," they can't go home.
- Unwitting Pawn: When they were summoned, and enslaved, they were told that the kingdom of Farmus was in desperate need of defenders from evil monsters. It's not until much, much later that they learn different, but being enslaved by Farmus, they have no other choice but to go along.
- Would Hurt a Child: Even children are not spared from their depravity.
- Break the Haughty: When he's fighting Hakurou outside the magical debuff and anti-magic barriers placed on Tempest, he keeps getting smacked down by the sheer difference in power and skill between the two of them. He can't bring himself to believe that the only reason he had a shot previously is that he was being helped by the two barriers over Tempest, until his head is sent flying, and he slowly, oh-so-very-slowly, starts to die...
- Cruel Mercy: Self-inflicted. After being beheaded, his head takes three full minutes to die, but that's not the worst part. His own skill, [Hyper acceleration] is still active during this time, making him see and process information at 300 times normal. That means, from his perspective, he's experiencing the world as a severed head, for fifteen solid hours!
- Eyes Always Shut: When he's goofing around and admiring his own self of superiority, his eyes look shut, as seen in the page image. When he has to get serious, he opens them all the way and starts going full-tilt Villainous Breakdown.
- Off with His Head!: How he dies, oh-so-slowly.
- Shut Up, Kirk!: As he's getting bested by the Kijin's best swords-man, and lectured on how he's in a clearly inferior position, he yells "shut up, old man" and then activates his [Hyper Acceleration] skill, hoping for a decisive blow in his favor. Unfortunately, there is a decisive blow alright, against him.
- Compelling Voice: She can use the power of her voice to buff allies or debuff enemies with certain orders.
- Logical Weakness: Her voice has to be heard to have an effect, so if there's a loud commotion going on, she's useless.
- Too Dumb to Live: While there's a battle going on just outside her tent, she completely lowers her guard and starts painting her fingernails, rather than preparing to run or hide. It gets her killed.
- Wrong Assumption: She presumed that since Shogou was coming into her tent, he'd won his fight. The real reason he was there was trying to run and hide. She winds up being killed by him to boost his own strength and recover from injuries he got from fighting Gerudo.
- Arrogant Kung-Fu Guy: Very, very arrogant. He presumes he can beat anyone in close-quarters combat, and those wearing armor or shields are cowards.
- Battle Strip: When he decides to get serious against Gerudo, he throws off his jacket. This proves a fundamentally bad idea.
- Dirty Coward: He loves to lord it over others when he thinks he's in the superior position, but when he's in the inferior position, he's shameless in running, hiding, begging, or doing whatever he can to prolong his own life.
- Hypocrite: He calls Gerudo summoning a second shield "a dirty trick" when he attacked helpless demi-humans, including women and children, inside Tempest, as they were weakened by not one, but two barriers, a monster-weakening barrier, and an anti-magic barrier.
- Karmic Death: He murdered Kirihara for a quick power-up. Razen murdered him to steal his body.
- Kick the Son of a Bitch: He murders Kirihara Mitsuni for a power-up. While this is still a horrific act, she was an asshole who didn't pay any attention to his clear wounds and did many horrific things on-screen.
- Psychological Projection: Since he's a complete coward, he angrily accuses Gerudo of being a coward for wearing armor and having a shield.
- Shut Up, Kirk!: While fighting Gerudo, he repeatedly yells "Shut up, Pig" as the latter was pointing out that this is a war, not a sporting event, and there's nothing "dirty" or "cowardly" about bringing your full might to bear on the enemy, or coming from an advantageous position against an enemy combatant.
- Villains Want Mercy: As Gerudo is pounding his face into mush, he repeatedly begs Gerudo to stop. Gerudo decides to grant mercy, alright, in the form of a Mercy Kill. Shogou runs away screaming in terror at the prospect.
- Wrong Assumption: When he starts pounding on Gerudo, with the latter doing nothing to retaliate, he presumes Gerudo's too overwhelmed by his sheer awesomeness to fight back. What's really going on is that Gerudo's using a [Corrosion] ability. He winds up looking at his limbs and realized he was basically punching a bag of formic acid.
Ten great Demon Lords (Later renamed to Eight Star Demon Lords)
Tyrant of Destruction
One of the most powerful Demon Lords, and one of the oldest. While she is flighty and somewhat scatterbrained, she is much smarter than she looks.
- Adaptation Dye-Job: In the original web novel she had white hair, in addition to a different outfit. The light novel and subsequent adaptations changed her hair to pink and gave her a more Stripperiffic outfit — though her hair turns white in her Super Mode.
- Authority Equals Asskicking: The ruler of her nation and the strongest member of it.
- Awesome by Analysis: Her Dragon Eye Skill allows her to gauge her opponent's magical energy even if they try to hide it, ensuring her opponent's can't pretend to be weak (or strong) in front of her.
- Badass Bystander: Milim lives in Tempest and doesn't make her identity a secret, but when Charybdis attacks the town, she offers to simply kill it (which she could easily do). Against Rimuru's wishes, the Oni convince her to let Rimuru fight it (he would rather simply have Milim get rid of it). The fight drags on for a long time while Milim simply watches it go down. Eventually the fight between Rimuru and the entity reaches a stalemate so Milim steps in blows it away with very little effort.
- Bare Your Midriff: This would actually be an understatement. She not only bares her midriff, but wears the bare minimum to cover up her private parts, with her buttocks actually showing.
- Barehanded Blade Block: Catches Shion's BFS with one hand and virtually no effort, despite the impact cratering the ground beneath them.
- Berserk Button: Calling her a "kid" generally results in people going flying or requiring large amounts of healing potion. It gets better when she starts to follow Rimuru's instruction that she should hold back, but people still go flying.
- Best Friend: She styles herself as Rimuru's "best friend," although this wasn't exactly a title she earned and more of a proclamation he couldn't refuse. It's also implied she ends up developing feelings for him.
- Black Knight: When she actually decides to take a fight seriously, she dons a set of jet-black armor.
- Blood Knight: Millim really enjoys fighting, and reacts to powerful opponents with a Slasher Smile and glowing Icy Blue Eyes. Rimuru immediately recognizes her initial borderline Cute and Psycho tendencies as a potential problem and takes steps to teach her restraint.
- Brutal Honesty: She both hates lies and being lied to, to the point she'll bluntly state her demands with no compromise and rampage if she's rejected.
- Cloud Cuckoolander: Milim is frightfully powerful and could easily level Tempest, but is easily manipulated into becoming friendly because she is an incredibly flighty goofball. When she arrives to test Rimuru, his fight with her involves throwing honey in her mouth because he could tell she was a weirdo that would react positively to sweets. This works.
- Costume Porn: Becomes quite a clotheshorse after settling in Tempest, being somewhat bored by her standard stripperific outfit.
- Curb-Stomp Battle: She ends Charybdis (a monster so powerful it clashes with Rimuru and Tempest for several hours in a stalemate without slowing down) with a single direct attack.
- Demon Lords and Archdevils: The second oldest Demon Lord after Guy.
- Ditzy Genius: Milim lacks even an ounce of common sense and is incredibly scatterbrained, but she's actually really smart and can easily outwit people trying to manipulate her. She's also capable of using magic so advanced, Great Sage can't even begin to analyze it.
- Dragon Ancestry: Daughter of the True Dragon Stellar King Veldanava and the human Lucia. This also technically makes her the daughter of the world's God.
- The Dreaded: All Demon Lords are feared by almost all of the world inhabitants. What sets Milim apart is that even other Demon Lords are afraid of her.
- Establishing Character Moment: She seems like a ditz at first. But she quickly arrives at Rimuru's village, causing a crater where she lands. Several of Rimuru's strongest fighters attempt to attack her since she seemed to be a threat, but practically everything they throw at her turns out into a No-Sell attack. Even Rimuru had to resort to trickery to "defeat" her by feeding her honey that she enjoyed so much she decides not to attack them in exchange for some more of it.
- Hartman Hips: Her Stripperific outfit leaving nothing to the imagination allows everyone to see her wide hips and rear contrasted by her petite, svelte form◊, which the anime and illustrations◊ likes to bring constant attention to. A official statuette was even made in her Boobs-and-Butt Pose illustration to emphasise her butt.
- Horned Humanoid: When she fights seriously and dons her armor, she has a horn out of her head like an ogre or oni.
- Idiot Hair: Has a prominent curved one, emphasizing her ditzy status.
- Incest Is Relative: Ends up falling for Rimuru in the finale even though it's heavily implied that he's a reincarnation of her father, Stellar Dragon Veldanava. That said, it should be noted Rimuru has no memories of his life as Veldanava (assuming he really is said reincarnation) and Milim herself barely knew about her father before his death anyways.
- Immortal Immaturity: Despite being one of the oldest and strongest being in the series, mentally she totally is the scatterbrained teen that her appearance suggest.
- Lamarck Was Right: The source of her incredible power is due to being the child of and named by the True Dragon Stellar King Veldanava, the first of the True Dragons and the original creator of the world. This allowed her to inherit a great majority of his power and partly why it was so easy for her to ascend to the rank of True Demon Lord.
- Lonely at the Top: She has had no friends for thousands of years due to her powers and because of the mortality of others.
- The oni originally attack her thinking she's going to attack Rimuru, but she casually counters everything they throw at her, culminating in her taking Benimaru's Black Flame spell dead on and letting it sputter out without a mark on her body.
- When she finally gets called in to battle Charybdis, the beast unleashes a Flechette Storm of its scales at her. She just lifts a hand and the attack just falls out of the sky.
- Pint-Sized Powerhouse: Looks like a kid, yet her strength is such that she can destroy entire kingdoms using nothing but physical power alone, to say nothing of her actual magic. When they first meet up, Great Sage informs Rimuru that even in a non-serious state, she has at least ten times the amount of power Rimuru currently has at his disposal, and this is after Rimuru got a power-up from devouring the Orc Disaster.
- Power Limiter: Rimuru gives her a pair of gauntlets that reduce her blows to 10% of their original strength. It says something about how strong she is that she can still sent opponents several times her size into the air pretty easily.
- Really 700 Years Old: Has the appearance of a twelve-year-old but is actually thousands of years old.
- Red Baron: She is known as the "Destroyer" due to her enormous physical and magical power, which is enough to decimate entire countries when she throws a tantrum.
- Semi-Divine: While she's not a Demigod like Chloe, Millim is the daughter of the multiverse's creator deity — making her hands-down one of the most powerful characters in the series.
- Seven Deadly Sins: Wields the Ultimate Skill Wrathful King Satan.
- Sir Not-Appearing-in-This-Trailer: An inverted example in the anime. She's seen briefly in the first ending seen in episodes 1-14. But she doesn't actually meet Rimuru until around episode 16, by which time a new op/ed is shown.
- Stripperific: Millim's usual outfit leaves almost nothing to the imagination and is little more than a tube top and low-riding panties.
- Super Mode: Her Battle Mode manifests black armor on her body, turns her hair white, and causes her to grow wings and a horn in the middle of her forehead.
- Through His Stomach: Basically how Rimuru "defeats" her in their first fight. He loads up a special attack, which appears to be a golden orb of power, and then smashes it into Milim's mouth. Said "orb" was actually just some honey he found, but she loved it so much that she was willing to consider their duel a "draw" and promises not to attack Rimuru's village or teammates, declaring Rimuru her "bestie" and Tempest to be under her protection.
- Unstoppable Rage: Is widely feared for it since she becomes unstoppable once sufficiently enraged to the point that only demon lords can stop her. Since her rage also converts to magic power thanks to her ultimate skill she virtually fight endlessly while being angry.
- Wake-Up Call Boss: Played With. At the time of her appearance, she's the first opponent who explicitly is many times stronger than Rimuru is...so Rimuru doesn't engage her in a fruitless battle to the death, but feeds her a bunch of delicious honey to calm her down and bribes her with more if she calls it a draw.
- Who Wants to Live Forever?: Rimiru theorizes that she chose a life of solitude so that she wouldn't outlive all her friends. This would also explain why she latched onto him so quickly, as the first (theoretical) immortal to show her kindness.
- World's Strongest Woman: Milim is the strongest of the Demon Lords and basically the strongest being in the world.
- Wrath: The embodiment of it thanks to her ultimate skill.
Emperor of Darkness
Supposedly the first and strongest Demon Lord.
- Authority Equals Asskicking: The ruler of his nation and the strongest member of it.
- Demon Lords and Archdevils: The first demon lord to ever exist.
- Hopeless Suitor: Amusingly, he's made offers to Leon for sex in both his male and female forms. Leon's rebuffed him every time.
- Meaningful Name: Named himself Guy after the scream his dying victims would give. Pissed off by that he was named Crimson by the first Hero after the color of his hair.
- Our Demons Are Different: Is the highest ranked demon, who in turn were originally known as dark elemental spirits.
- Older Than They Look: Despite his young appearance he is several thousand years old.
- Pride: The embodiement of it thanks to his ultimate skill
- Sorcerous Overlord: Rules over the northern continent where no life besides demons and monsters exist due to the environment being polluted by his magic power.
- Seven Deadly Sins: Wields the Ultimate Skill Prideful King Lucifer.
- Sex Shifter: Despite being a genderless spirit he has a male looking form for battle and a female looking form for operations. He himself notes the process of shifting between male and female form is so easy the question of gender is really irrelevant to him, though he uses male pronouns for convenience if nothing else.
- Took a Level in Badass: Was already powerful but gained more power after being defeated by Stellar King Veldanava and a second time after being named by Rudra.
- The Unfought: Held up as the strongest Demon Lord around and at least equal to Milim, but is never faced by Rimuru or his forces in real combat. Instead, he serves as an ally against Yuuki's forces and stalls against Chloe.
King of the Sleeping Forest
A fallen angel who became a Demon Lord.
- Brainwashed and Crazy: Velda exerts partial control over him by exploiting his old loyalty towards the true Veldanava, but when separated from his influence he breaks the control and is not happy about it.
- Dual Wielding: Wields Excalibur in one hand and Caliburn in the other.
- Demon Lords and Archdevils: One the oldest demon lords.
- Fallen Angel: Originally the highest ranked Seraphim of the angels but became a fallen angel later on after he went on a rampage when Veldanava and Lucia were killed and wiped out the nation responsible.
- I Am Not Left-Handed: Comes across as the weakest of the demon lords, but only if he isn't bothering to dual wield and is only putting in half effort as compared to zero or full power. At full power, he's the greatest swordsman on the planet. When completely lazy and working through minions, his Sloth ability would start building up massive energy reserves.
- Lazy Bum: The embodiment of it thanks to his ultimate skill
- Master Swordsman: The greatest swordsman of the entire world if he ever went serious.
- Older Than They Look: Despite his young appearance he is as old as the world itself, much like Guy Crimson.
- Our Angels Are Different: Originally a spirit of the light attribute that shifted into the dark attribute. Because of this, he can negate the weakness to light dark elementals normally have due to familiarity with said power.
- Seven Deadly Sins: Wields the Ultimate Skill Slothful King Belphegor. He's never shown using it right, though.
- Undying Loyalty: To Stellar Dragon Veldanava, the one who created him. So much so that his death was the reason he became a Fallen Angel.
A giant Demon Lord.
- Demon Lords and Archdevils: One the oldest demon lords.
- No-Sell: He's immune to magic apart from magic considered to be of a healing or restoration type, which Veldora exploits by using him as a fuel source for a land regeneration spell.
- Our Giants Are Bigger: Feared as the great Titan throughout the continent.
- Older Than They Look: One of the first living beings of the world.
- Physical God: His true form is that of a Titan and is regained by merging with his two brothers.
- Unskilled, but Strong: Noted to lack an Ultimate Skill, but is instead referred to as an Ultimate Being.
- Unstoppable Rage: His rages lets him increase his magic power and size
Ramiris of the Labyrinth
A fairy Demon Lord.
- Demon Lords and Archdevils: One the oldest demon lords, second only to Milim and Guy.
- Jerk with a Heart of Gold: She acts a little smug due to being both the Queen of Fairies and a Demon Lord, but has no problem in helping Rimuru after finding out why he went to the labyrinth.
- Master of Illusion: She's a master of mind affecting and illusion based magic, but has very little raw power because she's currently a child after reincarnating herself.
- Our Fairies Are Different: The queen of all fairies, reaching only a few centimeters in height.
- Older Than They Look: Several thousand years old and the third demon lord to ever exist.
- Squishy Wizard: She is a Demon Lord but a simple chop from Rimuru nearly puts her unconscious.
- Sweet Tooth: She really enjoyed the cookies Rimuru brought, and ate several despite them almost being as big as she is.
A self-proclaimed Demon Lord who instigated the whole Orc Disaster affair.
- Bad Boss: Thinks little of his underlings' wellbeing.
- Can't Catch Up: Clayman is one of the weaker Demon Lords and strictly speaking shouldn't count among the Ten, if not for his scheming.
- The Chessmaster: His skill for intrigue is the only reason that he is a Demon Lord, otherwise he'd be a fairly average mazoku.
- Circus of Fear: The Moderate Clown Troupe, a group of Mazoku doing hisnote bidding.
- The Dandy: Always sharply dressed, suave and elegant.
- Decoy Leader: Actually works as a front for his former boss and True Demon Lord, Kazaream.
- He Who Must Not Be Named: Gelmud always refers to him as "he", "his", "him" even in the midst of his breakdown, and Rimuru demanding to know who Gelmud's boss really is sends him into even more of a scrambling panic.
- The Man Behind the Man: His main modus operandi is to scheme and manipulate everyone around him with little regard of their own good.
- Monster Clown: As the leader of the Moderate Clown Troupe.
- Sharp-Dressed Man: His iconic white tux.
- You Have Failed Me: The moment Gelmud found that his scheme is failing at the seams, his main fear was Clayman's reaction.
A self-proclaimed Beastman Demon Lord who rules the Beast Country of Yuurazania.
- Abdicate the Throne: After Millim kicks his ass and Rimuru defeats Clayman, he decides to step down as a Demon Lord and becomes Millim's subordinate.
- Blade on a Stick: His main weapon.
- Blood Knight: He loves a good fight.
- King of Beasts: His true form and source of his Red Baron is a mighty lion lycanthrope.
- Odd Friendship: Eventually forms one with Gobta, due to the fact they both go through Millim's Training from Hell. In fact, he comes to see Gobta as something of a senpai.
- Our Werebeasts Are Different: He is a Beastman, a race of humanoid monsters that can change to their respective animals/beasts/creatures at will.
- Took a Level in Badass: After becoming Millim's subordinate and going through her Training from Hell, he becomes much stronger.
A self-proclaimed Demon Lord.
- Abdicate the Throne: After Rimuru defeats Clayman, she decides to step down as a Demon Lord and become Millim's subordinate.
- Anti-Magic: She can use magic jamming on her opponents.
- Harping on About Harpies: Resembles a classic harpy, with wings instead of arms and talons instead of feet.
- Mystical White Hair: Technically silver, but it does denote her power.
Blonde Devil / True Hero of Humanity
The Demon Lord who summoned Shizue.
- Bishōnen: Long gold hair, brilliant blue eyes, pale skin, and so handsome that he's often mistaken for a woman at first glance.
- Demon Lords and Archdevils: One of the youngest demon lords.
- The Hero: One of the three true Heroes of humanity but left them after several incidents to join the faction of Demon Lords.
- Holy Hand Grenade: Part of his abilities through his ultimate skill.
- Light 'em Up: Wields such powers due to his Ultimate Skill.
- Mis-blamed: In-Universe Shizue blames him for yanking her out of Tokyo firebombing and making Ifrit possess her, which brought her not inconsiderable suffering, but on the other hand she'd certainly die hadn't he summoned her, and Demonic Possession was the only way to save her from the horrific injuries she already sustained. Leon could've been less blase about it, though.
- Older Than They Look: Despite his young appearance he is three hundred years old.
- Seven Heavenly Virtues: Wields the Ultimate Skill Purity King Metatron.
Queen of Nightmares
The Demon Lord who rules over vampires.
- Back from the Dead: Can resurrect herself or other people back from the dead through her Ultimate Skill.
- Demon Lords and Archdevils: One the oldest demon lords.
- Elegant Gothic Lolita: Likes dressing this way. Other times she prefers dressing like a maid.
- Healing Hands: Has these powers thanks to the life-death reversal of her Ultimate Skill
- Mismatched Eyes: Her right eye is red while the left one is blue.
- Necromancer: Has these powers thanks to her ultimate skill.
- Seven Deadly Sins: Wields the Ultimate Skill Lustful King Asmodeus.
- Sitcom Arch-Nemesis: Veldora destroyed her original kingdom and she has never forgiven him, and all attempts to get on her good graces have ended in failure for the dragon. This doesn't help that Veldora accidentally reveals her name and her role as a Demon Lord in volumes 6 and 7.
- Vampire Monarch: Ruler of all vampires of the world.
Another human reincarnated into this world from the Tokyo Firebombings of World War II, she is a Summon who houses the soul of the Fire Giant, Ifrit, and bears a deep connection to Rimuru's fate...
- Cast from Lifespan: Overexerting her magic fighting a dragon caused her to age, though to be fair she is in her 70s-80s even if she appears otherwise.
- Cool Teacher: Actually the only one able to keep the Summons class in the Freedom Academy at Incracia in check. At least until Rimuru took over.
- Covered in Scars: Under her clothes she still has the burns from her summoning, and she only survived them because Leon had Ifrit possess her.
- Cursed With Awesome: She suspects her youth might be a curse from the demon lord but is happy with it.
- A Day in the Limelight: The anime has the entirety of episode 24 be dedicated to one of her past adventures, specifically detailing her meeting with the demon that would eventually be named "Diablo".
- Death by Origin Story: Her character is basically there to die and in the process give Rimuru a human form and a few plot threads like Leon Cromwell and the children in Ingracia. The light novel and further adaptations flesh her out a bit more, but the basics remain the same.
- Demonic Possession:
- When Ifrit originally took her over, he used her body as a vessel, but she was eventually able to take back control thanks to a hero and the use of her Anti-Demon Mask. However, recently, Ifrit began to regain strength thanks to her own own dwindling lifespan, and ultimately she falls back under it and forced to fight Rimuru. However, it should be noted that Leon did this specifically to extend her lifespan, as she wouldn't have survived the burns from her summoning otherwise.
- The anime also changes the nature of the possession to a minor extent. In the manga, Shizue completely lost herself to Ifrit upon her original possession and only regained herself thanks to being defeated by a hero and gaining her mask. In the anime/light novel, Shizune had more control, but Ifrit could usurp her against her will if he sensed a threat in Leon's presence. The amount of time she could go without wearing the mask without risking losing herself again to Ifrit is also much smaller in the manga.
- Flaming Sword: One of her preferred tactics is to wreathe her blade in fire to increase its destructive power.
- I'm Having Soul Pains: Due to the fact that Ifrit is slowly starting to regain control as her life nears its end.
- In-Series Nickname: "Shizu," which was originally coined by her summoner after she told him her name as "Shizu...e" and he took it as "Shizu E."
- Mask of Power: Her Cool Mask isn't just for show, it has anti-demon properties which helps her suppress Ifrit's influence on her mind and body. Rimuru eventually takes it as a Memento MacGuffin.
- Mind-Control Eyes: When they turn glowing red, that's when Ifrit starts taking over Shizue's mind.
- My God, What Have I Done?: Had a really bad one in the past when Ifrit took her over and made her torch her fellow child friend and her monster pet to ashes upon viewing said pet as a threat to Leon. (Anime/Light novel only; in the manga, once Ifrit is inside her she doesn't regain control for quite some time.)
- Oh, Crap!: Shizue has one every time Ifrit starts taking her over.
- Older Than They Look: She was reincarnated during World War II as a child, which would put her in her 70s to 80s, but she still looks barely over her mid-20s at latest. This actually helps her keep up a disguise along with her nickname of Shizu, as none of her fellow adventurers realize that she's actually the retired hero known as "The Explosive Monarch."
- Playing with Fire: Gains this as a result of her possession by Ifrit.
- Red Baron: When going by her real name of Shizue Izawa, she was known throughout the land as the "Conquerer of Flames", both because she had the flame spirit Ifrit possessing her, and because she maintained control over the spirit and utilized it's fiery powers to help others.
- Retired Badass: She's apparently been retired for 50 years according to the adventurers.
- Revenge: She hates Leon Cromwell for summoning her half-dead from flames, having Ifrit take over her body, and then abandoning her to fight a hero as a sacrificial pawn. Her desired goal before dying was to find and hurt him for all of it, and asks Rimuru to do the job for her as part of her Last Request. Of course, the truth is a bit more complicated than that...
- Scars Are Forever: Magic can't heal her burn scars because merging with Ifrit stabilized her body to its current state.
- Spit Take: Did one when Rimuru said he wasn't a bad slime because it reminded her of Yuuki talking about Dragon Quest.
- Together in Death: Gets reunited with her mother once she finally passes.
- Transformation of the Possessed: Happens to her when she fully loses control of Ifrit. She goes back to normal when Rimuru uses Predator on him and thus separates them.
- Wizards Live Longer: Stopped aging at 16 or 17 thanks to either Ifrit or the demon lord.
- Your Days Are Numbered: Despite her youthful appearance, Shizu is quite old, in her 70s at best, and is at the end of her life. She left her retirement to exact her revenge on Leon Cromwell for summoning her from her original world, but her trip was cut short as she had no more strength to contain Ifrit possessing her. Though Rimuru ended up beating the fire spirit quite handily, thus freeing Shizu, the strain of combat was too much for her (not to mention Ifrit actually keeping her alive all that time) and she died soon after the fight.
Spirit of Flame
The being inhabiting Shizu, a flame spirit called forth by Leon with a taste for death and destruction. Originally contained by Shizu using both her mask and willpower, it eventually breaks free and tries to resume it's desires, only to be thwarted by Rimuru.
- Call a Pegasus a "Hippogriff": Though fire-related, in mythology an Ifrit is a type of genie rather than a giant or titan.
- Doppelgänger Attack: Ifrit can summon copies of himself made of fire to overwhelm the opposition.
- Enemy Summoner: Ifrit can summon Salamander demons to aid him in battle, which breathe fire and can explode violently.
- Evil Is Burning Hot: He doesn't just have the ability to manipulate flames. His very body constantly produces intense heat, enough to melt rock just by touching it.
- Fiery Salamander: Can summon three of them in battle.
- Instant Runes: Can create a magic circle without chanting.
- Oh, Crap!: Ifrit gets several when he realizes his flames don't work on Rimuru, but his biggest is when he sees Veldora after he's devoured by Rimuru's Predator skill.
- Playing with Fire: As the one that provides Shizu with her power, he goes even further with it than her, having a variety of techniques involving the manipulation of flame.
- Scissors Cuts Rock: Ifrit and its Salamander summons' flames are so intense that Rimuru attempting to use Water Blade on them just causes it to erupt into steam without effect, and Great Sage informs him that while if he unleashed all the water in his body at once he could overpower it, the resulting explosion of steam would take out the entire goblin village in the process. This forces Rimuru to rely on using ice magic and his own immunity to flame to win.
- The Stoic: His normal expression is a indifferent grimace, with most of his fight only having him change expression when casting magic. That said, dealing with Rimuru and then Veldora causes him to lose his composure, expressing shock and fear.
Orc King/Orc Lord/Orc Disaster
Formerly a nameless Orc King who wanted to save his people from famine, he was granted a name by the demon Gelmund under the orders of the Great Demon Lord Clayman. Obtaining the Unique skill Starved, he was meant to become a Demon Lord capable of conquering and ruling the Jura Forest as their pawn.
- Adaptive Ability: As he's being burned by Rimuru's Flare Circle, he develops the Heat Resistance skill to tank the rest of it.
- Alas, Poor Villain: His death is portrayed as such. Rimuru killing him was clearly a Mercy Kill, to which the Orc Lord thanked him for allowing him to rest in peace.
- Anti-Villain: His people was starving, and he joined forces with Gelmund in order to save them.
- The Assimilator: His Starved skill functions similarly to Rimuru's Predator skill in that they both provide the potential for infinite growth by devouring others and adding their powers and skills to their repertoire.
- Authority Equals Asskicking: The leader of the Orcs and the strongest. While his soldiers were easily dispatched by Rimuru's subordinates, he was too strong for them, and Rimuru was forced to step up in order to deal with him.
- Benevolent Boss: Even after succumbing to hunger, he still loves his people. And while eating one of your own men for a power boost and healing would normally be a Moral Event Horizon, the orc in question willingly offered himself up and didn't struggle even as he was being devoured.
- Dragon Ascendant: Technically, he's already the Dragon-in-Chief for Gelmud and by extension Clayman, but upon deciding to take Gelmud's order to evolve to the Orc Disaster to heart, he chops Gelmund's head off and eats the corpse to do it, becoming the main antagonistic force for the arc.
- Expy: Of Ganon. Both of them are giant pig-man who became a warlord and demon king after they were driven to desperation watching their people suffer in a desert waste.
- The Good King: To the orcs. He was willing to abuse his Healing Factor and tear off his own limbs in spite of the pain to provide them some sort of food.
- Healing Factor: Not only does he possess regeneration and healing magic, he can also devour others to quickly restore his stamina. It's so potent Hakurou slicing his head off just slows him down and Rimuru is forced to use Predator on him to win (and even then, he resists it longer than any other creature before him). Even when he was still nameless, he didn't think anything of tearing off his own limbs and letting his starving people eat them since they would just come back.
- I've Come Too Far: He tells this to Rimuru. After eating his benefactor, his own brethren and even several others, he feels that he cannot afford to lose.
- I'm a Humanitarian: Since he can't absorb things like Rimuru, this is the only way Geld can actually use his Starved skill to the fullest. "Helping" is the fact it also gives him Horror Hunger so that he's not too picky about the act of eating anything in front of him.
- Kick the Son of a Bitch: Him killing and devouring Gelmund is not portrayed as horrifying to say at least.
- Knife Nut: Wields a large machete as big as a man...but compared to his own size it's practically just a butcher knife.
- Large and in Charge: By far the largest of all the Orcs, even before his ascension to the Orc Disaster.
- Power Copying: After devouring Gelmud, he gains the ability to use Death March Dance.
- Super Strength: He can match Shion's strength with ease.
- Unwitting Pawn: Subverted. He admits to Rimuru as he's being absorbed that he knew Gelmund was all but certainly using from the start, but he viewed the situation as a Deal with the Devil issue since to refuse would likely condemn his people to starvation.
- Wake-Up Call Boss: The first opponent Rimuru fights who legitimately provides a challenge. (Ifrit was only an issue due to Rimuru not remembering he had Heat Resistance and the risk of weaker bystanders, due to possessing powerful attacks that require dodging or intentional nullification instead of simply straight-up No Selling and possessing a ludicrous Healing Factor.
- Well-Intentioned Extremist: All he wanted was to save his people from a famine, no matter the cost. Rimuru promising to save them is what allows him to accept his death with grace.
- The Worf Effect: Despite taking a good amount of damage from their assault, he proves to be too strong for the oni and Ranga to best, showing the gap between them and a Orc Disaster. He then gets this at the hands of Rimuru, whose Predator Skill is superior to his Starved one.
A demon subordinate of Clayman of the Ten Great Demon Lords. Seeking to expand his master's dominion, he manipulated the various factions of the Jura Forest with the intent of conquering it all, only to find his plans coming apart at the seams thanks to one Rimuru Tempest...
- Asshole Victim: He manipulated the residents of the Jura Forest with the intent of letting them all get killed and/or eaten by the Orc Lord Geld to turn him into a Demon Lord, who in turn he always saw as a simple pawn. Absolutely no one feels sorry when Geld decides to kill and eat him.
- Be Careful What You Wish For: He yells at Geld to hurry up and eat his enemies to evolve into a Demon Lord. Geld takes his advice to heart and kills him, devouring his corpse to kickstart his evolution.
- Curb-Stomp Battle: His "fight" with Rimuru consists of his attacks getting nullified before Rimuru ties him up and rams his fist and foot into him hard enough to send him flying.
- Killed Mid-Sentence: He's so busy bragging about how Geld is going to kill Rimuru and his subordinates for ruining his plans he doesn't even notice Geld drawing back his blade for the killing blow.
- Malevolent Masked Man: He wears a Plague Doctor mask to hide his face. We never see what he looks like underneath it.
- Off with His Head!: How he dies, courtesy of Geld's butcher knife.
- Smug Snake: Far too confident in his plans for his own good, and far too confident in his power to think he'd last rushing right into the middle of the battlefield with people who want him dead. He quickly caves and yells at the Orc Lord to help him.
- Villain in a White Suit: Emulating his master Clayman, he dresses in a mostly white suit and hat to give off a fancy impression. He's an antagonistic demon.
- Villainous Breakdown: When he sees Rimuru's small force completely destroying the hundreds-of-thousands-strong Orc army, he starts breaking down in panic and fear upon realizing his head is on the chopping block with Clayman if he doesn't fix things, and thus he rushes to the battlefield. Once he gets there, he starts yelling in anger at them for getting in his way of creating a new Demon Lord and starts insulting everyone there, including the Orc Lord before going on the attack. When Rimuru No Sells his attempt and casually kicks his ass, he only gets worse as he panics and yells at the Orc Lord to help him.
- You Have Failed Me: He declares Gabiru is this for not dying and being eaten by the Orc Lord yet. He himself fears being on the receiving end of this from Clayman.
- Animalistic Abomination: It is a one-eyed vaguely shark-like monster — with ray-like wings in the anime, defies gravity, possesses enough power to wipe out a country, and was born from a cloud of Veldora's magicules — technically making it Rimuru's sibling.
- Curb Stomp Cushion: It withstands everything Rimuru's army throws at it and even fights Rimuru himself to a stalemate, but is effortlessly defeated by Milim.
- Demonic Possession: As a spiritual entity, it needs a host in order to manifest. Phobio is tricked into becoming its host by Tear and Footman.
- Dragon Ancestry: Indirectly, as it is an Animalistic Abomination spawned from Veldora's magical energy.
- Enemy Summoner: When summoned, it manifests a school of Megalodons — flying shark-monsters — using dragon corpses.
- Flechette Storm: It can fire its denticles/scales as razor-sharp homing projectiles.
- Gravity Master: It can manipulate gravity to enable itself and its Megalodons to fly.
- No-Sell: Its special ability, Magic Jamming, makes it immune to magical attacks.
- Roaring Rampage of Revenge: Owing to its host being Phobio, it attacks Tempest looking to kill Milim.
- Sealed Evil in a Can: It was sealed away by a hero in the distant past, though Tear and Footman trick Phobio into unsealing it and becoming its vessel by saying it will give him the power to kill Milim.
A group of five small children who, like Shizu, were summoned in order to turn into Heroes. However, because the process of summoning has some unforeseen consequences, the children now only have a few years left to live.
It is Rimuru's mission now to help the children move past their life expectancy, as Shizu's last desire.
- The Berserker: Ryouta Sekiguchi is usually quiet and timid, but his special ability sends him into an animalistic berserk state where he runs on all fours, clawing and biting at his opponents.
- Deity of Human Origin: Chloe's future self — who travels back in time to stabilize her child-self — is a Demigod, a divine entity surpassing both Heroes and Sages. Ramiris is terrified of her, though she does little more than kiss Rimuru and indwell her past self.
- Fusion Dance: Power Booster variation. They all go through this in order to stabilize their magicule levels with Superior Spirits.
- Heroic RRoD: The origin of their shortened lifespans. Summoned Otherworlders have an immense number of magicules but children do not usually inherit the Unique Skills necessary to put them to sufficient use. Pair that with the strain of containing such power on an immature body and children summoned to the Otherworld will eventually have their bodies destroyed due to their own power.
- Making a Splash: Chloe can control water to such a degree she can trap people in a sphere of swirling water and then form blades in said water to slice her victims apart.
- Marionette Master: Alice is able to levitate and manipulate dolls. Rimuru thinks to himself that she would be more effective if these dolls had claws, or if she could control other tougher stuff. Out of all the students, she was the one he was most initially impressed with, not that he would say that out loud.
- My Future Self and Me: Chloe is indwelled by the time-travelling divine spirit of her future self, which according to Ramiris creates a time loop.
- Playing with Fire: Kenya Misaki's introduction involves him launching a flaming Sword Beam at Rimuru the moment he enters S-Class, and complaining that he missed.
- Precursor Heroes: As part of the Timey-Wimey Ball she's stuck in, Chloe is part of a chain of heroes that goes Chloe —> Shizue —> Rimuru —> Chloe, making her a precursor to herself.
- Stable Time Loop: Chloe is part of a convoluted time loop, according to Ramiris. She's the Hero who sealed Veldora, who Leon was seeking to summon, and who Shizu admired and got her mask from in the past; having become a Demigod after countless time loops.
- Teacher/Student Romance: Chloe Aubert and Alice Rondo both develop Precocious Crushes on Rimuru, who laments that they should have waited until they were 18 or 20 to confess.
- Two Girls to a Team: Chloe and Alice are the only girls in the class, with the rest being boys.
- Your Days Are Numbered: They only have a few years left to live, since the magicules in their bodies will eventually collapse if nothing is done about them.