Demon King

The is the ruler of the Demon Clan. He is the one who handpicked the Ten Commandments and granted them their Commandments. He is also the father of Meliodas, Estarossa, and Zeldris, three of the most powerful members of the Demon Clan.

Appearance
The Demon King is shadowed in his first appearance, towering over Meliodas. In his first full appearance, he is seen as an enormous man with a full long curly beard. His height reaches the clouds and roughly equals that of a giant in stature.

He is armor-clad, wears a long partially torn cape, and a horned helmet. He also wields a massive sword.

Personality
The Demon King is fully devoted to the Demon Clan, seeming to put power and evil above all else, thus chastising Meliodas for throwing away his former life just for the sake of a woman. He has no empathy for subjects who go against the laws of the Demon Clan even if it is his own son, evidenced when he ruthlessly killed and cursed Meliodas for betraying the Demon Clan. The Demon King also is very serious in matters that involve the Demon Clan but is neverthless not without a dark and sarcastic sense of humor, as evidenced when he clearly taunted and mocked Meliodas.

The Demon King is shown to be considerably calculating and intelligent, as evidenced by his quickly realising that giving just a single Demon half of his power would mean threatening his rule and thus choosing to divide his power into 10 pieces to make sure he can still rule the vast and chaotic Demon World without allowing any challenge to his rule. It is also noted that the Demon King is unpredictable, even to his sons, as Zeldris noted he can never know what his father is thinking. When he makes up his mind, the Demon King will hear no objection from his subjects, even his own children, as not even Zeldris dared to disobey him when the older told him he will make Meliodas the new ruler of the Demon Clan. He seems to have some sadism, as he clearly took pleasure in the fact that Elizabeth's curse prevents her from being with Meliodas. In part with his ruthless nature, the Demon King has no tolerance for deception as he and the Supreme Deity unleashed a curse of fire and lightning that destroyed Belialuin when Merlin tricked him into giving her a blessing without her joining his clan. Despite his ruthlessly strict and harsh judgement, the Demon King isn't completely unforgiving and without mercy. While hostile and even mocking towards his traitorous son when he was in Purgatory, the Demon King was fully willing to crown his former favored, strongest son Meliodas as the new demon king when he had returned to his old self and was visibly pleased by this as well. Cusack even said that the Demon 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. In addition, rather than coldly dishonoring Estarossa for not being born with the abillity to manipulate darkness as well as being timid to the point he could only hurt an insect, the Demon King instead had enough compassion for his middle son to give him a Commandment.

History
Little of the Demon King's past is known. However, he would become the ruler of the Demon Clan and sire three sons, Meliodas, Zeldris, and Estarossa. Due to the chaos and massive size of the Demon Realm at his rule, the Demon King at first considered giving half of his power to his servant, but that choice was out of option as it could threaten his reign. To avoid giving too much power to someone, the Demon King chose to divide his power into ten pieces and gave it to the Demon Clan warriors he found worthy, thus creating the Ten Commandments. He also was noted by Monspeet to take pity on Estarossa when it was found that his second son was born without the power of darkness and decided to give Estarosssa a Commandment instead. While succeeding, it came at the cost of Estarossa being left mentally unstable as the Commandment slowly ate away at his mind and soul.

While originally having a treaty of peace with the Supreme Deity due to their similar power balance despite their opposite natures, 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.

3,000 years ago
After the betrayal of his son Meliodas 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 allied with the Human, Fairy and Giant Clan, thus unleashing the Holy War. 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 Beliauin in hopes of killing the girl in their anger, but the mage managed to escape with the help of her gifts.

During the last few days of the Holy War, the Demon King and the Supreme Deity having lost their patience in their shared anger and having had enough of their children's repeated defiance of the laws of their respective clans, so they 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 to the point of returning to be the bloodthirsty demon he once was.

Eventually, the Demon King, alongside the other members of the Demon Clan, were sealed away after losing the Holy War. While the rest of his clan was sealed in the Coffin of Eternal Darkness, the Demon King was imprisoned in the Purgatory.

Defensive Battle for Liones arc
After Meliodas's 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 counters that he is now free from the Commandments' bindings thanks to his curse, the Demon King agrees but mentions that he can feel Meliodas' quivering and expresses anger towards the certain woman who had changed Meliodas 3,000 years ago. He then informs his son that despite being greatly weakened, the curse he casted 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, 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 casually orders Zeldris to retrieve Meliodas and crown him as the new demon king and kill the Seven Deadly Sins before they become a threat. Zeldris reluctantly accepts and the Demon King reminds him that he observes everything from the Purgatory.

Abilities and Equipment
As the ruler of the Demon Clan, 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. Meliodas and Zeldris also inherited a portion of his strength, which was sufficient to make them the strongest of the Ten commandments. While he rarely fights, the Demon King possesses incredolous levels of combat might in battle, as despite having delivered half of his power, he proved capable of easily overpowering Elizabeth during the Holy War. 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, the Supreme Deity is the only being whose level of power is equivalent to the Demon King's: Meliodas also said that even his full power augmented by the power that Zeldris borrowed from their father cannot rival the Demon King's true power nor can he reach the Demon King's level of power by training for the time close to three days, so only can absorb the Commandaments.

Abilities

 * The Demon King is capable of bestowing a Commandment on those he deems worthy. By dividing his power at half, these Commandments are a fraction of this power and deliver a unique curse to whomever breaks a rule specific to each Commandment: Notably, these curses are not magical in origin, activating even when their holders are drained of magic, and are perceived differently than magic is as well.This increases the power of whoever is wielding them and if they were to be bestowed to individuals of a species different from Demons, the Commandments would turn them into Demons as well. It cannot be opposed even by its wielder, only those who also possess a Commandment or a Grace from the Supreme Deity are immune, with 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 gives their consent, or if they are powerless enough to being unable to fight or die.
 * Those who show faithlessness in the holder's presence will have their eyes set ablaze. It is held by Melascula.
 * Those who stand before the Commandment holder with hatred in their hearts will be rendered powerless to harm or inflict damage on anyone else. It is held by Estarossa.
 * Any who kills in the holder's presence will have their own time stolen from them, causing the victim to age rapidly and die. It is held by Grayroad.
 * The curse and its activation are unknown. It was held by Drole.
 * Any who turn their back to the Commandment's holder are treated as committing an act of treachery, are cursed into serving the Demon King and by extension the holder who is acting as the Demon King's representative. It was once held by Calmadios, but  is currently held by Zeldris.
 * The curse and its activation are unknown. It is held by Derieri.
 * The curse and its activation are unknown. It was held by Gloxinia.
 * The curse and its activation are unknown. It is held by Monspeet.
 * Those harboring greed, avarice and desire will be inflicted by its curse will lose their memories, feelings, and entire sense of self. It was once held by Gowther, but was later passed on to Fraudrin upon Gowther's disappearance.
 * This Commandment determines that any who tell a lie in the holder's presence will be turned to stone. However, only those who are aware that they are lying will be affected. It is held by Galand.
 * Admonition: The Demon King is capable of removing the Commandments he bestowed to others, as well as recovering the fraction of his power. He taught others how to do so, as he gave Meliodas and Zeldris the abillity to remove Commandments using the spell.
 * Curses/Blessings: The Demon King  is extremely proficient in the use of and curses and blessings, being capable of creating and casting the unique and permanent spells.
 * Capacity Transferring: The Demon King can transfer diferent capacities to other, including all the secret techniques of the Demon Clan to Merlin and lending a portion of his power to others, as he did with Zeldris when the younger demon became his representative. He also has the abillity to telepathically communicate with his youngest son even despite being sealed in Purgatory
 * Control Immunity: The Demon King can grant an individual with immunity to the possesion and brainwashing powers of the Goddess Clan.
 * Immortality Curse: The Demon King is capable of casting an incredibly powerful and permanent 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 King. The only way to dispel the curse is to get a power equivalent to the King himself or the Supreme Deity. The only known victim of the curse is Meliodas.
 * Nature Manipulation: Along with the Supreme Deity, the Demon King created a fog of death with fire and lightning capable of killing all the inhabitants of Belialuin.

Weapons

 * Large Boardsword: When he teamed up with the Supreme Deity to punish their children, the Demon King is shown to wield an enormous boardsword with a curved tip in similar concept to the large boardsword Meliodas wielded 3,000 years ago. It is safe to assume he is exceptionally capable with the sword, as he used it to easily kill Meliodas and break his giant broadsword.

Meliodas
The Demon King was once apparently fond and proud of Meliodas due to Meliodas's surpassing power and skill and acknowledged his power and also he considered Meliodas to be the most worthy and only heir to the throne. He also appears to trust Meliodas considerably as it is apparent that Meliodas had 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. However, their relationship became very strained when Meliodas betrayed the Demon Clan, as the Demon King was extremely angry for his betrayal, which caused the King to lose his worthy heir. As Meliodas continues to relentlessly defy the Demon Clan and the laws of his clan, their resentment for each other soon escalates to the point that the Demon King had no qualms killing his son and cursing him with Immortality to forever seperate him from Elizabeth and punish him for his defiance, something that made Meliodas strongly despise him, resulting in their extremely antagonistic relationship being mutual. Even centuries after, the Demon King and Meliodas's grudge and resentment for each other remained as strong as ever, evidenced when they both mock and taunt each other after Meliodas was briefly killed by Estarossa and descended to Purgatory. However, despite all that happened between them, the Demon King still considers Meliodas to be his son and the rightful heir to his mantle and throne and appears to be willing to fully dismiss Meliodas's former betrayal should he ever return, as evidenced when he openly revels in the idea of bringing his oldest son back to the fold and after Meliodas fell back into his former self, the Demon King was delighted and immediately ordered Zeldris to retrieve his elder son and crown him the new king of the demons, completely disregarding his son's betrayal and Zeldris' visible discontent and shock, even going as far as to chatisise Zeldris for his antagonistic reaction to his decision and sternly making it clear that he will not hear any objection of Meliodas's 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 reprensentative. Zeldris appears to respect his father greatly, but will not hesitate to talk something if it differs from his goals, though this rarely would change the Demon King's thinking.

Estarossa
The Demon King took pity on Estarossa as he was unable to be on par with the rest of his children in magic and power due to Estarossa being born without the ability to manipulate darkness, which is supposedly an innate ability of demons. The Demon King decided to instead give Estarossa a Commandment, but the plan backfired when Estarossa was left mentally unstable. Estarossa himself holds little respect for him compared to Zeldris', calling him the "old man" rather than father when he learned the Demon King still ordered Meliodas to be retrieved and crowned as the King of the Demons. In turn, the Demon King is fully aware of the side effects of giving his son the Commandment of Love and due to this, he is most likely aware of his son's hunger for power, as while he taught Meliodas and Zeldris Admonition, Estarossa was the only child he didn't teach how to remove Commandments.

Supreme Deity
Despite being mutual enemies from leaders of opposing clans, the Demon King teamed up 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 Meliodas, his heir, betrayed the Demon Clan. He evidently was sadistic pleased that Elizabeth's curse prevents her to be with Meliodas.

Memories of the Holy War arc

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

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