King of Chaos arc

The King of Chaos arc is the nineteenth arc in the series, lasting from the 335th chapter to the 343rd chapter.

Description
Shorly after Demon King's defeat, Merlin assembles the rest of the Seven Deadly Sins and reveals to them her own secret agenda: to break the seal on Chaos, an ancient and alpowerful entity within the deceased Arthur which resurrects him. Unexpectedly Cath reveals itself as a monstrous creature who craves Chaos' power for itself and tries to devour Arthur in order to achieve it. As result, the Seven Deadly Sins must help Merlin and Arthur so they can save the recent found peace in Britannia.

Fights and Events

 * Seven Deadly Sins & Arthur Pendragon vs. Cath Palug

Synopsis
The party celebrating the Demon King's defeat is held within Liones castle along with Elizabeth and the remaining Sins, but the onlookers notice the burn scar Merlin received from her kiss with Escanor and gossip over it, to the discomfort of the others and Elizabeth herself tells Merlin, if she wants, that it may be possible to erase the scar; Merlin asks if it's unsighlty but Elizabeth disagrees and believes it to be beautfiul along with the others.

As Diane relays how everyone, even Escanor in his final moments, has achieved their dreams, Diane realizes that Merlin is the only one who never revealed her goal. She claims that they'll help her if she needs it and Merlin decides to show them as they have a right to know and immediately teleports the other Sins and Elizabeth back to Lake Salisbury where they find the floating lake as well as Hawk and his mom who arrived after Zeldris' departure with Gelda.

The others are surprised as they didn't realize he was missing but Merlin tells them it's time to begin Arthur's awakening, to everyone's surprise. Using her magic, she brings Arthur's body with Excalibur running through his chest and asks the "priestess" if she is ready before a voice begins to come from the lake itself as it begins glowing from the immense amount of magic power it absorbed from Meliodas' attack that destroyed his father.

Suddenly, the magic from the lake bursts forth and goes through Excalibur and is seemingly absorbed into Arthur's body, blinding everyone in a burst of light until it dies down and everyone sees Arthur begin to awaken, having been brought back to life to Diane's enthusiasm but Meliodas feels something is off as Arthur wonders where he is before he is suddenly overcome is some kind of pain. Merlin is the asked by Meliodas what she did to Arthur, to which she responds her goal was to revive Arthur as the King of Chaos.

Arthur continues to lament about this unknown pain but Merlin tells him not to fear it as its now time for him to awaken his hidden magic, but Arthur doesn't understand what she's saying as he is suddenly overtaken by an unknown sensation as both his eyes turn pitch black with white iris and he screams out, with Hawk Mama suddenly opening her mouth and screaming in parallel to Arthur.

Meliodas flies up to Arthur as he believes something to be wrong but when Arthur sees him, he still believes Meliodas to be in his emotionless former self and declares he won't let the Demons have their way with Britannia before everything turns black and realiy itself seems to be deforming with Arthur at the center of the mayhem, along with Merlin at his side.

The Sins, Hawk, and Elizabeth are shocked and confused as to what they are seeing as Meliodas and Ban try to dodge strange monsters that appeared to be after the former before he hears Arthur quoting what he him back in the Vaizel Festival Tournament and cries as he asks why Meliodas betrayed everyone's trust. Merlin, however, hugs him and claims that Meliodas didn't betray them and calms him down, thus returning everything to normal.

While the others are wondering what they just witnessed, Arthur asks what Merlin is talking about before she and the others explain why Meliodas "betrayed" the Seven Deadly Sins and he realizes the error of his ways but is glad to see Meliodas wasn't in the right mind back then. With that said, Meliodas turns to Merlin and asks her what Arthur just did moments ago and what she keeps going on about. Merlin tells them about a being called Chaos, an ancient entity of light and darkness said to have created the world and the five races from nothingness, including the Demon King and the Supreme Deity, to Meliodas and Elizabeth's shock; she goes on to tell Arthur that as the "King of Chaos" he commands Chaos to his will and is the king destined to lead Britannia into a new world, much to his confusion and Meliodas' skepticism and slight anger when he asks why she would awaken a power that is both a blessing yet a curse and if that has been her goal the entire time.

Out of nowhere, the voice from before interrupts and says it will explain in Merlin's place. The others are suspicious of the voice as she refers to herself as the Lady of the Lake, an entity wrought from Chaos and who Arthur recognizes as the one who gave Excalibur to King Carfen thousands of years ago. Meliodas cuts her off by saying off his three thousand years of walking Britannia, he has never heard of a being called Chaos, especially from Merlin; the Lady of the Lake claims that is because Merlin has intentionally hid it from him, Elizabeth, and the others and Meliodas than asks what she means by that.

The Lady of the Lake begins by explaining Merlin's past, being born as a human child with a miraculous magic in the ancient city of Belialuin, the capital of wizards where the wiseman of humanity lived in prosperity and remained neutral in the Holy War, siding with neither the Goddesses or Demons. There, they secretly researched on human children with an unnaturally high aptitude for magic to use as secret weapons against the higher-ranking Demons and Goddesses, with Merlin being among them as a child.

Born to the capital's chief, her father, Merlin was a prodigy who already surpassed the adults in term of magic power but was a child who wanted her father's attention, yet all he did was give her tests to perform and never gave her any parental love, to her sadness. Tired of her suffering, Merlin ran away from her home but was chased after by the wizards due to her unique magic but to her surprise, she was saved by the leader of the Ten Commandments, Meliodas - the first person to offer her actual emotion and became the object of her affection.

Despite her infatuation with the young demon, Meliodas never returned Merlin's feelings due to his ultimately cold attitude and seeing her as a child. To win over his love, Merlin recreated herself into an adult woman but her hopes were crushed when she was introduced to the Godddess Elizabeth, Meliodas' lover. Caught up in anger, jealousy, and lovesickness, Merlin wanted to unleash all her pent-up hate on the two, but was unable to bring herself to truly hate either of them.

Returning to Belialuin of her own voliiton, Merlin dedicated herself to her studies in an attempt to block out her feelings with knowledge, but no amount of studying could fill her aching heart and her days were spent troubled, until the day when she heard the wisemen gossiping about Chaos, the drive of power born amidst ancient stars far away.

The legend spoke that Chaos first created the world and all its creatures before bearing two offspring of light and darkness: the Supreme Deity and Demon King, and finally the Sacred Tree as its third offspring. These three godly beings would each go on to create their own realms as well as their own races to serve them. Following this, Chaos created the Giants as the fourth race but was disappointed with them due to being slaves of their own power and cowardly in their inability to reject fighting and war.

It was then that Chaos decided to create Humans, which it put both positive and negative feelings into, thus giving them a contradiciting nature similar to that of itself and made them its favorite creation. However, the Demon King and Supreme Deity became envious of their creator as well as fearful that the love and reverence their own creations gave to them would eventually be stolen by their creator. To prevent this, the two gods joined forces to seal Chaos away and thus allowing them to feared as the most powerful beings in existence.

Upon learing this, Merlin made it her goal to resucitate Chaos and bring it back into the world, by spending the next three thousand years structuring her life around this single purpose, as she believed the entity would finally be able to fill the aching void in her heart with its limitless unknown.

Everyone is shocked to hear this as the Lady of the Lake continues by saying to accomplish this goal, Merlin used the Seven Deadly Sins but that was merely evenining the ledger as they used her plenty of times as well. Diane, however, has enough and tells the Lady of the Lake to keep quiet as she doesn't know anything about them and despite not knowing much about Merlin herself, that she is still one of the Seven Deadly Sins; their friend.

The Lady of the Lake confirms this as she doesn't know Merlin personally but does know that Merlin is the one who gave the Giant craftsman Dabuzu the idea for forging the Coffin of Eternal Darkness to ultimately seal away the Demon King and Supreme Deity from Britannia. Not to mention that she intentionally delayed her spell to stop time as to allow the Demon King to possess Meliodas' body, as well as reactivated Elizabeth's curse after Meliodas broke it, and finally tricked Meliodas to diverting the combined magic into Lake Salisbury as part of her plan.

Diane refuses to believe it out of hysteria while King tells Merlin to speak for herself, to which she reveals further that to revive Chaos, it wasn't as simple as sealing away the two gods; one of them had to be completely destroyed as to upset the balance between light and darkness. Ban realizes that coincides with the Demon King's desire to have Meliodas' body and how she helped him. She also states that another requirement was an immense amount of magic power in order to allow Arthur to absorb Chaos itself and the others realize that everything the Lady of the Lake has told them is, in fact, true.

Meliodas then demands Merlin if she actually tried to kill Elizabeth as part of her plan and she says that if he broke the curse on her and himself, he wouldn't have a reason to kill his father and claims she couldn't allow that, to Diane's horror and Meliodas' anger for dangering Elizabeth's life and also for using her friends as a means to an end and King himself claims he doesn't understand Merlin or her actions out of anger.

The Lady of the Lake claims this to be human nature, as to both love someone yet hate them at the same time and wonders due to them being different races, could ever truly understand each other?

Meliodas reprimands Merlin for her actions due to the possibility that Chaos could be a horrible monster or just doesn't exist at all. The Lady of the Lake counters by stating Chaos is a real entity and, to their confusion, they have already met it several times. Nobody understands at first but then she tells them they have ridden upon her back throughout their adventure and the others, minus Hawk, realize her to be referring to Hawk Mama, whose eyes appear to be pitch black and hollow.

Hawk laughs at the idea, refusing to believe his mother to be the "Chaos" they've been talking about but notices his mother hasn't moved at all before she suddenly deflates on herself and collapses into a pile of skin, to everyone's shock as Hawk rushes over in horror. King himself realizes that Hawk Mama isn't a pig at all but is just layers of moss built upon itself as is an empty shell. Arthur is confused and wonders where its content, Chaos, went to which Merlin claims it's inside of him now as it switched hosts once Arthur was revived.

Arthur himself is in shock as he believes the "giant green pig" to be inside of him but Merlin assures its Chaos and Meliodas realizes the power Arthur used unconsciosuly was Chaos itself and tells Merlin to return Arthur to normal but claims she can't do that as Chaos itself chose Arthur to be its new host. Before a conflict can brew between the two of them, Arthur intervenes as they shouldn't fight over a "baby chick" like him, to which an actual baby chick appears due to Arthur's using Chaos' power again unconsciously.

After seeing what he has made, Arthur is astounded and wonders where these new buildings and landscape came from but suddenly a part of the Boar Hat is broken apart and Cath appears, glad to see Arthur is alive. However, the Lady of the Lake is horrified when she sees Cath appear and fearfully tells Merlin not to let it near Arthur, but before anyone can react, Cath attempts to devour Arthur whole and only fails due to Meliodas pushing Arthur out of the way yet realized Cath was successful in tearing Arthur's right arm off as he screams out in agony.

The others are shocked and horrified to see Cath attack Arthur for no reason but the Lady of the Lake reveals the monster cat's identity as Cath Palug, a tyrant beast born from the Mother of Chaos who desires Chaos' power itself and challenged the almighty entity once yet lost and was eventually sealed by the Goddess Clan for its misdeeds.

Story Impacts

 * Arthur is revived and becomes the King of Chaos.
 * Merlin and the Lady of the Lake reveal the existence of Chaos, the entity that created the gods, the five races, and the world itself.
 * Cath is revealed to be the monstrous Cath Palug, a tyrant beast born from the Mother of Chaos who desires the power of Chaos itself, by devouring Arthur and succeeds in devouring his right arm.
 * Arthur tries to reason with the monster, who explains it only protected Arthur to take his power once awoken, but is temporarily defeated by the young king using a reformed Excalibur.
 * Merlin attempts to cut ties with the others, thinking she can no longer be their friend, but they return to help her and Arthur when Cath returns in it's final form.
 * Arthur declares to Cath that he will rebuild Camelot as an "everlasting kingdom" and absorbs the monster, accepting his position as the King of Chaos, with Meliodas and the others supporting his new goal.