Assault Force vs. Zeldris, Chandler & Cusack

Assault Force vs. Zeldris, Chandler & Cusack is a battle between the Assault Force of the allied forces and the Demon Prince Zeldris, alongside the highest-ranked demons Chandler and Cusack.

Prologue
When arriving at Camelot, the Assault Force discovers the castle covered by an enormous sphere of darkness, product of Meliodas absorbing the Commandments. Ludociel invokes his Sanctuary, creating an Ark barrier around him, Merlin, Escanor, Hendrickson and Gilthunder, being able to enter the space of darkness thanks to Melascula's Commandment that wants to enter and join the others.

Battle
Upon entering they find the cocoon of where Meliodas is in, the five are received by Zeldris, Cusack and Chandler. Ludociel, Escanor and Merlin go face to face with Zeldris, Chandler and Cusack respectively, while Hendrickson and Gilthunder are overwhelmed by the presence of demons.

When the battle begins, Escanor attacks Meliodas' cocoon, and while the demons are distracted by this, Merlin assaults them with Double Impact. When they emerge unscathed and attack her, she notes that Chandler and Cusack's power far exceeds that of the Ten Commandments. Escanor moves to protect her but is thrown back by the two demons' combined attack, forcing Merlin to repel them with the second stage of her spell.

Ludociel assaults Cusack and Chandler with his Grace. Ludociel happens to confront Zeldris, noting that his sword speed is the fastest in all of the Demon Realm. After a swift exchange of swords, Ludociel receives a cut on his cheek, while Zeldris receives the same injury plus a large cut on the arm. Ludociel calls him rude for hurting a woman's face. He is later saved from Cusack's attack by Hendrickson, Ludociel calls him an idiot for trying to save him when he had already read his attack, but still appreciates his concern for him and heals the wound he received on his leg.

Ludociel intercepts the advance of Zeldris with Gold Shining. He is slightly surprised when Zeldris emerges unscathed, assuming it must be the magic power of the Demon King.

Zeldris then proceeds to use his original power Ominous Nebula, creating an incredible force of attraction, which draws the Assault Force towards him. Zeldris claims that they must get out of their way, releasing an attack that leaves Ludociel, Escanor, Hendrickson and Gilthunder wounded against the wall. Zeldris creates another force of attraction, but Escanor and Ludociel manage to hold on to it, while Hendrickson and Gilthunder are kept away in safety by Merlin's teleportation.

Ludociel is carried away to attack Zeldris, sure to have deciphered Zeldris' sword technique. However, is only repelled and embedded against the wall as last time. After being attracted again, Ludociel clings to Escanor to sustain himself. Merlin declares that Zeldris has an attack from which it is impossible to defend himself and on top of that resistance to both physical and magical attacks, which will make the battle harder than they could have imagined.

Ludociel uses Ruby Shine to blind Zeldris with a bright light while Escanor causes a huge explosion with Cruel Sun to camouflage their presences. Convinced that Zeldris will not be able to counterattack without being able to anticipate them in the same way that Full Counter, Ludociel and Escanor launch themselves on him, but to his surprise both are rejected in the same way once again.

Ludociel does not fully understand why his attack does not work when he is once again absorbed into Zeldris' vacuum, who declares that it is time to stop wasting time and get serious, then increase the pressure and speed of his power. Merlin is finally sucked by his power but is protected from Zeldris's blow by Escanor, who enraged by the fact that Merlin was injured, releases '''Crazy Prominence.  Seeing how Zeldris manages to avoid the attack, as well as destroy a huge debris that falls on him, Merlin finishes deciphering the true nature of the Ominous Nebula''', calling it so simple and yet unparalleled in its brutality.

Ludociel returns to attack Zeldris, creating a great Ark sword in his arm. He remembers how he sacrificed everything, his love and friendship, in order to fulfill his duty to win the Holy War. However, Zeldris repels him once more, being Gilthunder who saves him by receiving the attack himself, but being both crushed against a wall.

As Escanor decides to fight Zeldris, he ask Merlin to hold on for a minute. Merlin says the she is done with mistakes and uses Cho-renzoku Teleport to acquire enough speed to teleport herself and Hendrickson out of Zeldris' power. Escanor, reaching the power of The One, manages to advance without being absorbed by the Ominous Nebula. Seeing such a fact, Cusack asks if he is some kind of monster.

Escanor attacks him with Rhitta. However, the Ominous Nebula manages to repel his attack, but only causing Escanor a few scrapes in the arm. Seeing a tiny nick on Rhitta, Escanor drops his weapon. Escanor uses Divine Sword Escanor, colliding with the Ominous Nebula that is unable to repel it. Zeldris increases the power of his Ominous Nebula, managing to push back Escanor. However, the power of Escanor ends up being superior, breaking his Ominous Nebula and forcing Zeldris to intercept him with his sword. Zeldris is forced to retreat, however, Escanor denies to let him flee and attacks him with his Divine Spear Escanor, piercing his chest with his finger and leaving him very wounded. As Escanor prepares to finish him off, Chandler manages to create an artificial night and Escanor is returned instantly to his night form.

Ludociel manages to take advantage of the second Zeldris would have take to reactivate his God power, to obliterate it again with his Gold Shining, this time, managing to wound him. When Ludociel was about to finish Zeldris off, Cusack intervenes by stopping the Archangel with his swords. As he takes the heat in a fight with Cusack, Chandler decides to take charge himself of Merlin and the others.

Merlin fires Exterminate Ray, to which Chandler responds with the same spell. However, Chandler's Exterminate Ray is much larger and more powerful than Merlin's. When Chandler's  Exterminate Ray begins to take the upper hand, Merlin uses Enchant: Infinity so that her attack grows with infinite magical power, surpassing Chandler and managing to hit him.

When Ludociel is pushed back with several wounds, Chandler and Cusack initially does not believe Merlin's words about creating weaknesses in them, claiming that none of her attacks have the slightest effect. However, Chandler is suddenly assaulted by a lightning strike, at the same time that Cusack is hit by a concentrated wind. Both are surprised at the damage that those attacks caused them. Merlin goes on to reveal that it is the Double Impact she used previously, which is actually an attack combines the magical attributes of the four elements and multiplies it, which allowed Merlin to discover which elements were most vulnerable, being for Chandler the lightning and for Cusack the wind. Also, the second wave of the Double Impact is a spell that decreases the resistance of the opponent and thanks to her Infinity, the resistance of both will continue to decrease with each attack.

Chandler tries to use Absolute Cancel to undo Merlin's magic, but before he can do so he is assaulted by another lightning attack, injuring himself more than with the previous one. While trying to perceive from where the attacks are coming from, Cusack receives another attack. Merlin reveals that her Infinity causes endless and untraceable magical powers of lightning and wind to continue dancing and reacting to every movement or magical invocation they make, assaulting them until they die. Ludociel asks what kind of bizarre magic it is, with Merlin claiming that she does not understand it well either; she took a dual element attack magic, attributing it "invisibility", "undetectability", "automatic tracking" and on top of that, she casted Infinity. Escanor asks her when she came up with all this, and she reveals that she thought about it while using teleportation to escape from Zeldris' Ominous Nebula.

As Chandler and Cusack continue to be stricken by attacks, Cusack refuses to accept that the most powerful demons are being humiliated by a mere human. Then he manages to use Resonant on Merlin. Getting inside Merlin's subconsciousness, he sees her true appearance. Cusack mockingly threatens her saying that she will suffer the same fate as Arthur, but not before she nullifies her barricade of attacks. Cusack is suddenly receives a single punch in the face. Merlin, free of any control, tells him that it was foolish of him to think that she could be taken over, reminding the demon that she got the blessing of the Supreme Deity, on top of the strengthening of her soul and spirit as well. Cusack's soul begins to be slowly tortured by Merlin's consciousness, who mutilates him with snake-like creatures. Merlin praises his resistance to so much pain that it would have destroyed the mind of any other demon. Merlin declares that the only way she can fill her heart after losing Arthur is inflicting torment and agony on Cusack, and mutilating his soul until the point where he can no longer return to normal.

Zeldris tries to protect Chandler form the magic attacks with his God, but his wounds gives Ludociel the chance to finish him off with his Ark blade. When the battle seems be won, the spell that Gowther had used 3,000 years ago began to fall apart and all who kept their memories altered realize that "Estarossa" was actually the Archangel Mael.

Ludociel's mind is in shock and he is emotionally shattered. While Merlin suffers the stress of the spell breaking, Cusack takes the opportunity to escape from her mind. When Escanor worries about Merlin, she tells him to take the opportunity to take Rhitta. Thanks to this, Escanor resumes his daily form. However, all this gives time to Cusack, Chandler and Zeldris for recover completely.

Cusack and Chandler declare that it is their duty to take charge of the enemy for Zeldris to save his power to face the Seven Deadly Sins. Seeing no other way to defeat the likes of Merlin and Escanor, Cusack and Chandler decide to combine into a single entity known as the "Original Demon", the original form from which both demons was divided into after trying to dethrone the Demon King.