Demon King

The is the ruler of the Demon Clan, as well as the one who handpicked the Ten Commandments and granted them their Commandments. He is also the father of Meliodas and Zeldris, two of the most powerful demons and the two strongest members of the Ten Commandments.

Appearance
He is a robust man with a full long curly beard. His height reaches the clouds, even greater than that of any Giant in stature.

After trying to stop Meliodas emotions from escaping he lost his right arm in skirmish with him.

He wears a giant armor, a long partially torn cape and a horned helmet that cast a shadow over his eyes with the demon clan symbol on it. He also wears black gauntlets in both his hands and a massive sword sheath to contain his large broadsword.

Personality
Fully devoted to the Demon Clan, the Demon King is very serious in matters that relates to his clan and puts them above all else, forcing worthy demons to become his allies against their will and chastising Meliodas for abandoning his former life just for his lover's sake while showing disgust at the 'effeminate' nature of his emotions. Due to his devotion to the laws of his clan, the Demon King is fully willing to punish any demon who betrays the clan even if it is his own children, evidenced when he ruthlessly killed and cursed Meliodas for his betrayal. He also doesn't tolerate betrayal from his allies, ordering Zeldris to execute the entire the Vampire Clan for their revolt.

Due to his ruling position, the Demon King has no tolerance for deception as he and the Supreme Deity unleashed a fog of fire and lightning that destroyed Belialuin when Merlin tricked him into giving her a blessing without her joining his clan. When he makes up his mind, the Demon King will hear no objection from his subjects and even his own children, as Zeldris didn't dare to disobey him when his father told him he will make Meliodas the new ruler of the Demon Clan. It is also noted that the Demon King is unpredictable, even to his sons, as Zeldris said that he can never know what his father is thinking. The Demon King appears to be even more demonic than his son was, as shown by how Meliodas's emotions angrily called him out when the Demon King deemed him as the destroyer of his plans for the true Meliodas to become his heir again, saying "You Are the Destroyer!"

Due to his nearly unmatched power, the Demon King has extremely high levels of self-confidence that borders on arrogance, openly telling Meliodas, Ban and Wild that there is no way they can pass through the door of Purgatory as long as he guards them, even telling his defiant son that he is the one who decides all that happens in Purgatory. Despite his confidence, the Demon King takes any battle seriously, attacking any foe no matter the level of their strength relentlessly without holding anything back, showing that he doesn't underestimate his enemies. This is probably due to the knowledge that only Supreme Deity can match his power and thus almost any other opponent wouldn't provide him any entertainment enough for him to toy with them or that he prefers to quickly finish any battle he takes part in. However, the Demon King is not above taking pleasure in intense battles, as shown by how he smiled after Meliodas figured out the nature of his magic, and he is also not above praising his opponents even though he is quick to also mock them for their failure, as shown by how he admits to being impressed when Ban, Meliodas and Wild attacked him again after being decisively beaten for over 60 years but taunts them for not understanding they didin't have any ability able to harm him. Despite his seriousness, the Demon King seems to have a sarcastic sense of humor that varies depending on who he is talking with: When talking with those he disliked, his sarcasm can be ruthlessly straight to it, taking time to mock Meliodas on his defeat and simply returned his bluffs on the curse's advantages himself put on him by taunting him on the much more heavy disadvantages of the Immortality Curse. With those he is on good terms with, his sarcastic sense of humor can be casual, such as when his youngest son was visibly angered by the fact Meliodas was still chosen to be the new King of Demons so sarcastically rebuked Zeldris by saying that he shouldn't call his brother a traitor anymore and instead welcomed him with open arms as now that Meliodas has returned to them. However, his arrogance was what led to his inability to prevent Meliodas's emotions from escaping. The Demon King was confident that only with his true magic power can Meliodas put up any of a challenge against him but his fears made it impossible for him to tap into it, only to be proven wrong when Meliodas uses all his power and destroys his arm. At which point, the Demon King was so shocked and desperate to prevent it that he did no actual action rather than demand his son's emotions to not go back.

When up against an opponent he particularly holds anger towards, the Demon King seems to be willing to brutalize said foe first rather than immediately killing them, left his son bloody and effectively unable to fight back before easily killing him at Holy War, apparently venting out his immense rage at his son for his betrayal. He also isn't above taking pleasure over the suffering of those who he dislikes, as he clearly was pleased by the fact that Elizabeth's curse prevents her from being with Meliodas. Furthermore, the Demon King isn't above mocking his opponents should they fare poorly, taking the time to laugh as Meliodas and Ban could only dodge his attacks.

Despite his ruthless attitude and harsh judgment, the Demon King isn't completely unforgiving and without mercy: While hostile and even mocking towards his traitorous son when he was in Purgatory, he was fully willing to crown his former favored, the strongest son Meliodas as the new demon king when he had returned to his old self and was visibly pleased by this. Cusack even said that their king was being far too compassionate with Meliodas and even noted he did this because he still considers Meliodas as his son despite their mutually antagonistic relationship. Later on, during his fight with Meliodas, Ban and Wild, he offered them a chance to peacefully leave his presence after demonstrating how much more powerful he is compared to them. In addition, the Demon King didn't punish Zeldris for just sealing the Vampire Clan due to being unable to bring himself to kill Gelda, implying that he wouldn't punish his children for an only trivial setback. It can also be assumed that he might not have minded Zeldris's relationship with Gelda due to her being an ally with his clan unlike Elizabeth whom separated from his son along with her own mother and his rival, having some sympathy for his youngest son when he couldn't bring himself to kill his former lover and hence why he was willing to allow him to seal the Vampires away instead of killing them like he originally ordered.

History
Little of the Demon King's past is known except that he is the first demon king. Due to the chaos and massive size of the Demon Realm at his rule, he originally was considering to give half of his power to his servant, but that choice was out of option as it could threaten his reign and instead divided his power into ten pieces in order to give it to the Demon Clan warriors he found worthy, thus creating the Ten Commandments.

At some point, the Demon King created a certain demon, denominating him the Original Demon, to gave him his power and made him his retainer. When the Original Demon rebelled against him, the king defeated him and, as punishment, split his body and soul into two beings: Cusack and Chandler. Then made them the tutors for his two sons to train them in combat and raise them as candidates for the throne.

The Demon King's army constantly clashed against the Supreme Deity's, but their forces were too equal and thus decided to have a treaty of peace the despite their opposite natures. However, the peace was unfairly broken by the Supreme Deity's subjects and fellow goddesses, who damaged even the civilians from the Demon Clan. These actions made both rulers fall in rivalry again.

3,000 years ago
After the betrayal of his son Meliodas for his alliance with his angelic lover Elizabeth and the death of two of the Ten Commandments at the latter's hand during his escape, the Demon Clan entered the war with the Goddess Clan, who took the chance to defeat them by cooperating with the Human, Fairy and Giant Clan. These events were known as the Holy War, which caused the Vampire Clan to revolt against the demon ruler due having always despised being ruled by him. However, the Demon King personally crushed their rebellion and ordered his executioner to exterminate the defeated Vampires, including his beloved Gelda, although he let Zeldris seal them away instead.

Having heard about a girl from Belialuin who possessed infinite magic though, the Demon King dealt with her at the same time as the Supreme Deity in order to put the girl on his side: When the girl told them that she would follow the one who gave her the best blessing, the Demon King gave her all the knowledge of the magic of the Demon Kingdom as well as immunity to the possession and brainwashing of the Goddesses. Being deceived by the girl who rejected them both taking their blessings, the Demon King and the Supreme Deity destroyed Belialuin in hopes of killing the girl in their anger, but the mage managed to escape with the help of her gifts.

As a result of the forbidden spell used by Gowther, the memories of the Demon King were altered to believe that the Archangel Mael was his second son "Estarossa", feeling pity for him when it was found that his second son was born without the power of darkness and his reputation as a timid coward unwilling to hurt even an insect, which made every demon except Meliodas laugh at him and eventually decided to give Estarossa a Commandment instead. It came at the cost of Estarossa being left mentally unstable as the Commandment slowly ate away at his mind and soul though.

During the last few days of the Holy War, the Demon King and the Supreme Deity had lost their patience in their shared anger due to their children's repeated defiance of the laws of their respective clans, so worked together and fought against Elizabeth and Meliodas, easily killing them and cursing them for eternity. The Demon King cursed Meliodas with immortality as his punishment, reviving him every time he died, in exchange for his emotions being consumed more and more so himself can feed on them and his son return to be the bloodthirsty demon he once was.

The Demon King and the other members of the Demon Clan were eventually sealed away after losing the Holy War. While the rest of his clan was sealed in the Coffin of Eternal Darkness, he was imprisoned in the Purgatory. However, the Demon King continued to observe Meliodas from Purgatory through the eyes of different animals that became his companions, later sending a creature from Purgatory to perform that function. Ever since then, Wild, the brother of the creature, has challenged the Demon King to battle to escape Purgatory and reunite with his brother for 120,118 times, but the Demon King always dealt him a crushing defeat each and every time they fight.

Defensive Battle for Liones arc
After Meliodas' fight with the Ten Commandments, the Demon King greets him in Purgatory.



He admits to having been keeping an eye on the captain of the Seven Deadly Sins throughout and muses that even Meliodas was unable to do anything other than wait for death when caught by the Commandments of Piety and Love. When Meliodas counter mocks him by saying that he is now free from the Commandments' bindings thanks to his curse, the Demon King is unfazed and agrees while also revealing that he can feel Meliodas' quivering and expresses anger towards the certain woman who had changed Meliodas 3,000 years ago into the shadow of his former self he is now. He then informs his son that despite being greatly weakened, the curse he cast on the Dragon's Sin of Wrath would allow him to feed on his emotions every time he dies, allowing the Demon King to regain his lost power and at the same time reverting his traitorous son back to the state he was three thousand years ago.

Prelude to the New Holy War arc


After Meliodas fight with Escanor, the Demon King senses that his son has started to return to his former self, much to his delight. He contacts his youngest son and representative, Zeldris, and shows no interest when Zeldris expresses he will find the one who killed the demons guarding Camelot, and instead telling Zeldris that while his seal is not yet broken, Meliodas will now replace him as the rightful heir to the throne of the demon king. Despite Zeldris obvious shock and visible anger and discontent, the Demon King sarcastically rebukes his calling Meliodas a traitor, as Meliodas shall now be welcomed as the new Demon King. Although Zeldris tries to reason with his father, the Demon King sternly silences Zeldris by saying he will not hear any objection to Meliodas's rule and crown him as the new demon king and kill the Seven Deadly Sins before they become a further threat. Zeldris reluctantly accepts and the Demon King reminds him that he observes everything from the Purgatory.

New Holy War arc


In the Purgatory, the Demon King appears threateningly looming over the emotions of Meliodas, Ban, and Wild when Meliodas said that he has no memory of Estarossa. Revealing that he too can not remember anything about his middle son, the Demon King disgustingly said that the effeminate nature of Meliodas' emotions made him sick and his son has no need of the existence of these.

Wondering on how Meliodas' emotions returned to his original form and why he and Ban got there, the Demon King quickly realizes that Wild guided them and deduced that they have learned on the existence of the portal to the living world. Wild bravely charges at him, saying that he will finally force through the Demon King alongside Ban and Meliodas, but the King effortlessly flicked him away with a single finger. The Demon King then began pressuring Meliodas and Ban with quick slashes, declaring that they will never return to the living world and soon cutting off Ban's arm.



After commenting on the Demon King's massive power, Ban attempts to steal the King's power, but the Demon King's Magic Power repels the assault back to Ban, instead of absorbing Ban's power for himself. He continues overwhelming Ban and Meliodas with his sword while laughing mockingly at Ban and Meliodas for their efforts. The Demon King is soon attacked by Wild but remaining completely unfazed; he merely grabbed and almost crushed him with his fingers before throwing him away while admonishing them for not giving up, confidently saying that as long as he guards the door, it is impossible for anyone to pass through the door. Not fazed by Meliodas' comments that he is not the one who decides that, the Demon King corrects his son that he is the one who decides everything in Purgatory and unleashes several strikes of thunder at Meliodas, but Meliodas Full Counters it. Remaining unfazed by it, having absorbed it with his magic power, the Demon King gives them the choice of continuing to fight and be killed or to flee, but the king suddenly asks on what Meliodas knows on Estarossa, as he cannot remember him while he remembers all that happened as well as every member of the Demon Clan. When Meliodas tells him that while Estarossa was his son, he was born without the power of darkness and a weak-hearted coward who could not even kill a single insect, the Demon King completes that part by saying that he took pity on him and gave him a Commandment, shocking Meliodas. The Demon King then realizes that Gowther is behind this as he was the only Commandment who betrayed the King and the only one who can do so.



For 60 years, the Demon King effortlessly continues to overpower his son's emotions, Ban and Wild, all the while looking unperturbed as he blows them far away. When they come to rechallenge him, the Demon King admits to being impressed by their bravery and tenacity but rebuffs them for not having learned anything, as his physical constitution makes any attempt of Wild to harm him utterly futile. Additionally his ability The Ruler can easily counter Ban's attempts to steal his powers instead make him even more mighty and the Full Counter possessed by Meliodas also does not affect him due to him just absorbing the redirected magical energy. Before knocking out Meliodas and blowing away Ban and Wild too, the Demon King notes that Meliodas's Full Counter is just a weak copy of Chandler's magic power. Only with his original magic power can he even hope to fight against him but mocks him for being too afraid, hence making it impossible for him to use it.



Later on, when Ban uses his Snatch again, the Demon King is exasperated by how Ban has not learned that any attempt to steal his power is futile. However, he finds that Ban has learned to "give" instead and as his magic power is inversion rather than absorption, the Demon King is weakened. As Meliodas points out the truth of the King's incredulous magic power, he is unconcerned, instead actually feeling it would alleviate his boredom, but insists that he will never let Meliodas's emotions leave Purgatory.

As he attempts to attack them again, the damage inflicted by Ban being only mediocre and not any hampering, Ban uses the full extent of his immortal life-force to stop the King to buy time. However, the King reverses the inversion aspect of The Ruler and instantly recovers. He easily grabs Ban in his hand and slowly crushes him while being intrigued at how Ban can offer slight defiance. Unfazed when Meliodas saves Ban, apparently activating the full extent of his powers, the Demon King is not at all willing to let Ban and Wild pass the gate even without Meliodas's emotions and attacks, but Meliodas surprisingly deflects it.



Infuriated, the Demon King rages on how Meliodas defied his father, but Meliodas coldly told the King he is no longer his father but is not able to understand why he keeps referring to Meliodas's emotions as a failure. The two trade blows, with the Demon King parrying every blow with his massive sword with ease while telling his son it is because of Meliodas's emotions destroying his plans of passing on the mantle of the King of Demons into his son, which Meliodas scoffs at, telling his father he is more of a destroyer than Meliodas ever was. Soon, the King gets the upper hand, forcing back Meliodas with a slash despite his attempts to parry before submitting him with another sword blow. He muses on how while Meliodas is the only worthy being of his throne, his emotions are unnecessary and prepares to kill him. However, he is suddenly slightly injured by Wild, shocking him as he looks at the beast. Wild holds the Demon King back with all of his life force and power while pushing Meliodas and Ban to the gate. The King quickly regains the upper hand and forces Wild back, killing him finally, but the attack on the King has brought enough time, and his son's emotions and Ban successfully escapes.

The Demon King manages to grab Meliodas towards the exit with his arm, stating he will never allow him to return to the real world. However, the Demon King's arm is severed, surprising the Demon King that his son has used his original magic power with the power of harming him. The Demon King says that he can not go back because he will ruin all his plans, contenting Melidoas when he first saw his face of anguish

Abilities and Equipment
As the ruler of the Demon Clan and the most powerful Demon, the Demon King holds terrifyingly massive amounts of power, with just possessing a fraction of his power made the Ten Commandments among the strongest demons in existence. According to Meliodas when saying on how to lift the curse on him and Elizabeth which can only be done by someone as equally powerful as the Demon King or more, the Supreme Deity is the only being whose level of power is equivalent to the Demon King's. His prodigious son also said that even his full power augmented by the power that Zeldris borrowed from their father cannot rival his true power nor can he reach the Demon King's level of power by training for the time close to three days with true rivals, so only by absorbing all Ten Commandments can he be equal to the King's immense power. While he rarely fights, the Demon King possesses unparalleled might in battle even after having delivered half of his power, with Meliodas himself said that he was utterly powerless before his father and was killed effortlessly by him in the Holy War. He was also capable of single-handedly stopping the rebellion of the Vampire Clan, defeating and leaving them at the mercy of his executioner Zeldris. He utterly defeated Wild in all of their countless altercations and effortlessly outmatched Meliodas's emotions, Ban and Wild at once for 60 years without sustaining a scratch. Even after managing to form a counter for the King, in the end, the Demon King was too powerful and only with Wild sacrificing himself was Meliodas and Ban able to escape.

Immortality: Unlike other regular Demons who can only live for 1000 years, the Demon King seems to have an indefinite lifespan as he has lived in Purgatory for hundreds of millions of years without showing any changes to his status despite how Purgatory's time is vastly faster than on Earth. It's possible that he granted immortality to himself as he did with Meliodas.

Enhanced Durability: The Demon King's physical resilience and durability are immense, being completely unfazed by Wild's Guruguru Wild attack. His resilience and durability likely contributed to his ability to easily survive inside Purgatory despite its extreme environment.

Enhanced Strength: The Demon King also has monstrously massive levels of physical strength, effortlessly flicked Wild away with a great force that tore apart the ground into it using a single finger when the latter charged at him quickly and later effortlessly stopped his attempts to drill him with only two fingers before effortlessly throwing him away.

Master Swordsman: Despite his large size, the Demon King has been seen to hold considerable levels of great agility and speed. Combined with his vast levels of skill and experience, the King can effortlessly wield his giant broadsword with a single hand with extreme finesse, able to deliver devastatingly fast and strong slashes that can effortlessly cut through landscapes. This even easily pressured the extremely fast Ban and Meliodas into the defensive and cut off Ban's arm while the latter himself was barely able to dodge the attack. Later on when he engaged Meliodas in a one-on-one swordfight, the Demon King easily had the upper hand and quickly defeated him.

High Intellect: The Demon King is shown to be considerably calculating and intelligent, quickly realizing that giving just a single demon half of his power would mean threatening his rule and chose to divide his power into ten pieces so he can still rule the vast, chaotic Demon realm without allowing the challenge. He eventually chooses to use a creature from Purgatory to keep watch over Meliodas after realizing that creatures from the living world are far too weak and less long-lived. From realizing that Meliodas too does not remember anything related to Estarossa, the Demon King realized that all the memories held by the demons on Estarossa were forged and quickly deduced that it must be the demon Gowther due to the nature of the former's powers. He also appears to have a perfect memory recall, although it can be tempered with by sufficiently powerful means, saying he remembers all the days he spent in both the Demon Realm and Purgatory as well as all his minions and the Goddess Clan vividly and only forgotten memories related to Estarossa due to the demon Gowther's influence.

Abilities

 * The Demon King's eponymous magic ability that also goes by his own name. It allows the user to invert all the attacks sent at him, including Meliodas and Ban's Full Counter and Snatch abilities. All attacks and weakness are converted into healing and fortification. Even the effects of others' powers are completely reversed; per example, when Ban tried to steal Demon King's energy, he was forced to give his own to the ruler. However, as The Ruler functions on the concept of magic inversion rather then magic absorbtion, any magic ment to strengthen him or increase his power will instead weaken him, as shown by Ban. Despite this weakness, he can easily overcome it by deactivating his own power of inversion.


 * After dividing his power in half, the Demon King granted ten fractions of this power portion to ten elite warriors, which delivered a unique curse to whomever breaks a rule specific to each of them. Notably, these curses are active even when their holders are drained of magic, so they can be perceived as different compared to normal magic. This increases the power of whoever is wielding them and if they were to be bestowed to individuals outside the Demon Clan, the Commandments would turn them into Demons as well. It cannot be opposed even by its wielder; only those who also possess a specific immunity such as another Commandment or have received Divine Protection from the Supreme Diety are immune, while the curses will only be lifted if the victim defeats its wielder or at the victim's death. The Commandments can be withdrawn from their wielder if they give their consent, if they are powerless enough to being unable to fight or if they are dead.


 * Curses: The Demon King is exceptionally accomplished in the use of curses, being capable of developing and casting highly unique yet powerful and durable spells.
 * Immortality Curse: A curse that revives the victim without fail regardless of the means of death, including suicide or getting killed, no matter how many times they die. It additionally prevents the victim from dying of old age. In exchange for the infinite number of revivals, the victim's emotions are slowly drained to nourish the user. The only way to dispel the curse is to get a power equivalent to the King himself or the Supreme Deity, if not superior. The only known victim of the curse is Meliodas.


 * Nature Manipulation: The Demon King has powerful control over the elements, causing a fog of death as well as fire and lightning capable of killing all the inhabitants of Belialuin along with the Supreme Deity. On his own, the Demon King was able to send out several strikes of thunder at Meliodas with a single hand movement.


 * Manipulation Immunity: It can grant an individual with immunity to the possession and brainwashing powers of the Goddess Clan. This negation spell was used on Merlin.


 * Power Transference: The user can transfer different powers to others, including all the secret techniques of the Demon Clan and lending a portion of his power to others. This supporting spell was used on Merlin and Zeldris when the younger demon became his representative and obtaining the power God.


 * Unknown Telepathic Power: The Demon King has the ability to telepathically communicate with his representative even while still sealed in Purgatory. Through unknown means, the Demon King also can see through the eyes of creatures, even from other worlds like Hawk. According to Meliodas, his father used to keep watch over him to make sure he carried out his duties via the creatures around him.

Weapons

 * Large Broadsword: The Demon King wields an enormous broadsword with a curved tip in a similar concept to the large broadsword Meliodas wielded 3,000 years ago, but it is much larger. It is strong enough to easily kill Meliodas when later was at his full power and break his broadsword.

Meliodas
The Demon King once was very fond and proud of Meliodas due to his surpassing power and skill, greatly acknowledging his power and considering him to be the most worthy and only heir to the throne. His trust of Meliodas is displayed by the fact that Meliodas learned Admonition, from the Demon King considering that Zeldris, the King's Representative, was the only other demon seen able to use the spell to remove Commandments aside from certainly the Demon King himself. His heir was initially loyal enough to his father that he relentlessly did battle with the Goddesses every day and night despite how foolishly he thought of the war between the Demon and Goddess Clan was. This changed after he met, fell for and allied with the Goddess Elizabeth, deciding to betray the Demon Clan and killing two Commadments in the escape. This made the Demon King extremely angry for losing strength and lose his worthy hair, which made their relationship very strained. As Meliodas continues to relentlessly defy the Demon Clan and his laws, the Demon King's resentment for his oldest son soon escalates to the point that he finally engaged him personally, which ended in utterly defeating Meliodas and subjecting him to a brutal beating, ruthlessly killed and cursed him with Immortality to forever separate him from his lover and punish him for his defiance, something that made Meliodas strongly despise him and resulted in their extremely antagonistic relationship being mutual.

Even centuries after, the Demon King still retains a grudge and resentment for Meliodas, although he shows it much more subtly and as he is able to see right through his elder son, he is one of the few able to remain entirely unaffected by his son's bluffs, evidenced when the Demon King only lightly mocked Meliodas after he was briefly killed by Estarossa and descended to Purgatory in which his son openly bluffed in front of him of the advantages of his curse which he was unfazed by and calmly pointed out the disadvantages of Meliodas's curse and how he can feel Meliodas's immense rage and fear coming from him to taunt him. Despite feeding from his emotions, the Demon King despises how effeminate Meliodas became after falling for Elizabeth, openly saying that he was disgusted by it and feels that Meliodas has no need for the existence of his emotional self. He shows extreme rage of how far Meliodas had fallen in his eyes when he angrily yelled at his son's emotions for having defied his father and considers him to be only a danger that will destroy his plans for the true Meliodas to ascend to the throne. However, the Demon King still considers Meliodas to be his son and the rightful heir to his throne despite all that happened between them, appearing to be willing to fully dismiss Meliodas' former betrayal should he ever return and in fact actually having always planned to revert Meliodas back to the Demons, delightfully reveling the idea of bringing his oldest son back to the fold and says that Zeldris should rejoice as Meliodas will finally return to the Demon Clan after he fell back into his former self and sternly making it clear that he will not hear any objection of Meliodas' rule.

Zeldris
The Demon King and Zeldris have a fairly good relationship, with he giving his youngest son a portion of his magic power to use and considering him his representative. Zeldris appears to respect his father greatly, but will not hesitate to protest against something if it differs from his goals. This this would rarely change the Demon King's thinking though, so Zeldris will still carry out his father's orders anyway, showing great loyalty to his father.

Gowther
The Demon King once acknowledged Gowther's power as a magician enough that he forced him to become a member of the Ten Commandments. When Gowther defied him, the Demon King imprisoned him and seems to despise him for that. Zeldris has said that his father is extremely angry upon learning Gowther escaped and his anger towards Gowther seems to increase even more after learning he had tampered with his memories, calling him a "damned bastard".

Chandler
The Demon King's exact relationship with Chandler is unknown but he clearly respected Chandler's abilities considerably, considering how he let Meliodas study under him. He acknowledged Chandler's prowess in Full Counter as being much greater than Meliodas, as shown by how he admonished his son's emotions for his Full Counter moves as being just a weak copy of Chandler's.

Cusack
The Demon King's exact relationship with Cusack is unknown but he seems to respect Cusack's compotence, as he allowed Zeldris to study with him. Cusack is loyal to the Demon King but though he would carry out his orders even if unwillingly, he is not above showing dissaproval of it.

Supreme Deity
Despite being mutual enemies from leaders of opposing clans, the Demon King teamed up with the Supreme Deity to punish their children during the Holy War for their continued defiance to the laws of their respective clans, showing that they are capable of working together when the situation demands it.

Elizabeth
The Demon King has a strong resentment and hatred for Elizabeth as she is why his heir Meliodas betrayed the Demon Clan. He evidently was sadistically pleased that Elizabeth's curse prevents her to be with Meliodas, as shown when he laughed when referring to the curse Elizabeth was under.

Before the Series

 * Demon King vs Wild: Win (120,118 Times)

Memories of the Holy War arc

 * Meliodas and Elizabeth vs. Demon King and Supreme Deity: Win

New Holy War arc

 * Meliodas, Ban & Wild vs. Demon King: Win (+6093 Times)

Trivia

 * So far, the Demon King is chronologically the oldest being in the series. By being in Purgatory, where one minute is a year, that would make his 3000 years spent there would lead to his age being over 1,576,800,000.

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