Cusack

is the highest-ranked demon of the Demon Clan as well as Zeldris' former master.

Appearance
Cusack is a tall and very muscular man with red hair that has bangs extending to cover his right eye and end in a long ponytail braided. He also sports a very long mustache that reaches his pectoral section and a small goatee.

His demon mark consists of two black arrows extending below his left eye and a spot of darkness on his right shoulder that extends further around his arm.

His attire consists of a skin tight white vest shirt with no sleeves, black pants and high knee boots. On his forearms are detached sleeves.

Upon revealing his true form, Cusack grows much taller in stature and his arms grow longer and his hands become larger, enough to hold both his sword hilts in between his fingers. His hair and mustache also grow and turn white. The color of his eyes are inverted. He also grows dragon-like wings from his shoulders. His demon mark is larger that extends down his cheek with the arrows converging together and a mark grows on his chest forming a cross.

Personality
Cusack is very confident in his abilities, requesting Zeldris' permission to exterminate the Seven Deadly Sins, former Fairy King Gloxinia, and former Giant King Drole all by himself.

Like Chandler's attachment to Meliodas, Cusack is very much attached to his student, Zeldris, expressing the utmost confidence and loyalty to the Demon King's second son. This extends to the point that he believes Zeldris to be worthy of reigning the Demon Clan next instead of Meliodas. This attachment led him to express complete anguish and shame along with rage when he ranted about how he failed to protect Zeldris when Meliodas pinned him down upon his arrival to Camelot.

Despite being a loyal vassal of the Demon Clan, Cusack is shown to be quite critical towards some of them as he outright called the Demon King being too compassionate with Meliodas in spite of his betrayal. He also denounces Chandler as being incompetent when he and Meliodas returned to Camelot with Elizabeth still alive despite it being Meliodas' orders.

In battles, he swiftly brings down opponents as efficiently as possible as shown with Cath but will toy with them should he be bored enough and also if he is curious about them. He is also rather patronizing towards them if he notices distinct flaws about them as he lectured Arthur Pendragon on why he failed to win the battle like intended.

Cusack is shown to be proud of his mustache, claiming it as the number one mustache in the Demon Clan and was even shocked after realizing half of it was cut off in a fight.

History
Long before the Holy War, Cusack trained Zeldris, the second son of the Demon King in combat.

Cusack rarely fought during the war 3,000 years ago. Eventually he along with the rest of the Demon Clan were sealed away within the Coffin of Eternal Darkness by the allied clans (Goddess, Giant, Fairy, and Humans).

Prelude to the New Holy War arc


After Zeldris claims that he is the most worthy to be the next Demon King, Cusack, along with Chandler, walks into the scene. Cusack says that he can see Zeldris on the throne of the Demon King, and he wants to help him by offering his strength. He then bows down and explains why it took so long for them to get out of the seal. He apologizes for eavesdropping on Zeldris' conversation with the Demon King, and requests Zeldris' permission to exterminate the Seven Deadly Sins, Gloxinia, and Drole. Zeldris tells him to stand and says that Cusack and Chandler will fill the void of the other nine Commandments. He replies that he is not worthy of his praise. Chandler says how jealous he is that Zeldris and Cusack get to have a student-master reunion. Cusack tells him not to worry because they get to serve the demon army once again, and reveals that he is Zeldris' former master and Chandler is Meliodas'.

When Zeldris reveals his father's plan to retrieve Meliodas to make him the new Demon King, Cusack is reluctant, wondering what the Demon King's intent may be after that, to which Zeldris responds in ignorance. When Estarossa awakens momentarily from his coma, Cusack shows concern for his presence, knowing of his mental instability.



After the departure of Chandler to rescue Meliodas, Cusack stays in the castle to stay with Zeldris, something that the latter finds suffocating, although this does not bother Cusack. When Zeldris mentions that the Seven Deadly Sins should not be underestimated, Cusack claims that Chandler is still in a position to finish them. During a tea that Zeldris finds disgusting, he comments with Cusack that things will get out of control once Chandler returns to his true form.

When Meliodas returns to the Camelot along with Chandler and Elizabeth, Cusack receives them along with Zeldris. Cusack recriminates Chandler's incompetence for allowing a goddess to be with them, causing him to get upset. When Zeldris jumps to attack Meliodas but is subjugated by this one, Cusack immediately goes furious to help him, but is impaled by the dark matter of Meliodas, who tells him to stay out of his affair with his brother. Then, Meliodas continue to convince Zeldris to help him become the Demon King, leaving Cusack in shock.



Outside the castle, Cusack curses his weakness and his inability to help Zeldris, recriminating Chandler for the actions of his apprentice, without it being important. When asked why Zeldris is helping Meliodas, Peronia approaches him and says something to his ear. Sopprived, Cusack leaves the castle saying he has something to do.

The next day, when Zeldris returns from his quest if he has managed to retrieve Melascula's Commandment, Cusack avoids Chandler questions about his actions the last night. Cusack is unhappy to hear that the Four Archangels had been awakened.

When Arthur Pendragon infiltrates the castle in search of the holy sword Excalibur, Cusack and Zeldris discover it. Cath rushes to distract them to allow Arthur to escape, surprising Cusack with his telekinetic powers. However, both quickly defeat Cath and stop Arthur from reaching the Excalibur. Meliodas appears telling them not to kill Arthur while ordering him to leave. When Arthur manages to brandish Excalibur blinded by the wrath of Meliodas' betrayal, Cusack is stunned when Arthur manages to avoid Chandler's Extermiante Ray and cut him in half with a technique he should not know. There, Arthur quickly attacks Cusack by cutting his body in three parts and recovering Cath.



While Arthur was facing Meliodas and Zeldris, Cusack and Chandler appear safe and sound, revealing that they were only allowed to attack to test the power of Excalibur. However, Cusack is stunned to see that his mustache had been cut, regretting having lost it. He then unleashes his aura alongside Meliodas, Zeldris and Chandler, intimidating the heroes inside Excalibur. There, Arthur suffers a sudden fall of strength and falls to the weakened ground. Cusack approaches and lectures him on his mistakes, revealing that even though he is the bearer of the sacred sword, he has not nearly the strength to resist the power of the heroes of the past through it and thus he has completely self-destructed. He also points out that his second mistake was to face four highest ranking demons, who have no reason to fear even mighty human heroes unlike a lesser demon. There, he uses his Resonant to put Arthur under his control.

While deliberating on how to kill Arthur, Merlin suddenly appears in front of him and uses her Icicle Castle to catch Cusack on ice. Cusack manages to free himself, but Merlin manages to escape along with Arthur and Cath.

Chandler reprimands Cusack for allowing them to escape, admitting Cusack that he was somewhat careless. However, he declares that he will finish Arthur there. Using the connection created between them by the Resonant, Cusack forces Arthur to pierce his own heart with Excalibur, preventing him from releasing the sword until his heart is completely destroyed.

New Holy War arc
While a whole army of demons gets ready for the new Holy War, Chandler and Cusack prepare for it by releasing their true forms. Cusack says that with the seal of the goddesses almost completely broken, everything is ready to go, saying that they will unravel what they are capable of due to their old age.

While the war is unleashed, Cusack is seen in Camelot with Zeldris guarding the cocoon in which Meliodas is carrying out the process of absorbing the Commandments.

While waiting for Meliodas to come out of the cocoon, Zeldris, Cusack and Chandler are met at the castle by the Assault Force. The three demons are faced with Escanor, Merlin and Ludociel. Cusack personally confronts Merlin.

After evading the attack of Escanor, Merlin assaults them with Double Impact. When they emerge unscathed, Cusack and Chandler attack Merlin together, being intercepted by Escanor. After removing him, Merlin repel them with the second stage of her spell. Surprised, the two demons are attacked by Ludociel, receiving a multitude of attacks to such high eloquence that they are not seen, ending up embedded against the wall. Cusack complains that his old body takes time to warm up. Cusack is enraged when Zeldris is wounded in a clash of swords with Ludociel, attacking him with his darkness. After being separated by Hendrickson, Ludociel uses his Gold Shining against Zeldris, with no effect on this one. Chandler and Cusack depart when he adopts the position that will release his original power, worrying both demons. Cusack says the the two of them will no longer necessary once Zeldris take action.

Zeldris then proceeds to use his original power, Ominous Nebula, creating an incredible force of attraction, which draws all living beings towards him. Chandler and Cusack manage to avoid being drawn into a wall. Seeing how Merlin manages to use his teleportation to stay out of Zeldris' power range, Cusack says she only delays the inevitable.

During the battle, Chandler and Cusack receive collateral damage from Ludociel's Ruby Flash and Escanor's Crazy Prominence. While the Assault Force is incapable against Zeldris, Cusack tells them that they should stop resisting and only die. But nevertheless, when Escanor releases the power of The One, Cusack becomes confused as he becomes able to walk over Zeldris' power as of nothing.

When Ludociel was about to finish Zeldris off, Cusack intervenes by stopping the Archangel with his swords. When Cusack asks Zekdris to let him take care of him, he agrees as long as he does not allow anyone to disturb Meliodas. Zeldris tells Cusack to make them understand the true scope of his and Chandler's power as the demons of the highest rank and superior to the Ten Commandments and himself. When Cusack tells him that he will be the one to surpass him, Zeldris does not understand what he is referring to.

Cusack is engaged in his fight with Ludociel, exchanging powerful and rapid blows between his swords and Ludociel's  Ark blade. In the end, Cusack manages to destroy Ludociel's clothes, with Cusack boasting of having been the one who taught Zeldris to use a sword. Ludociel manages to strike him in the abdomen surprisingly warning him not to get cocky, but Cusack manages to resist without injury and responds with a headbutt. Seeing that Ludociel's power is weak compared to his original body, Cusack deduces that this is the limit of the human vessel.

After he pushes Ludociel back with many injuries, Cusack and Chandler advance after being hitted by some magical attacks. There, they both get attention as Merlin begins to gather magic. 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 wind concentration. Cusack is surprised at the damage that those attacks caused him. 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 Cusack the wind. Also, the second weave 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.

Cusack as Chandler 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 magical powers of lightning and wind to continue dancing and reacting to every movement or magical invocation they make, assaulting them until they die.

Cusack continues to be stricken by wind attacks and can not do anything. Cusack refuses to accept that the most powerful demons are being humiliated by a mere human. There, he laughs as he manages to use Resonant in Merlin. Walking inside Merlin's subconscious, seeing his true appearance, Cusack affirms that she will suffer the same fate as Arthur after he has nullified his barricade of attacks. Claiming that he will lament in hell for opposing the most powerful demons, Cusack gives back to Merlin the ability to speak, but is then bet up by a simple fist of Merlin's consciousness. This tells him that it was foolish to think that she could derail her will knowing that she can strengthen her mind thanks to the blessing of the Supreme Deity. Merlin claims that Cusack will feel all of Arthur's resentment.

When the spell that Gowther had used 3,000 years ago began to fall apart due to Meliodas and the Demon King discovered the truth, Cusack, like all those who were under its influence, begin to suffer the effects of the spell that kept their memories altered. Thus, Cusack realizes that "Estarossa" was actually the Archangel Mael.

Abilities and Equipment
As Zeldris' former master and the highest-ranked demon, Cusack is extremely powerful. Zeldris states that along with Chandler, he is more than enough to fill in the nine vacant spots of the legendary Ten Commandments. According to Arthur Pendragon, his power rivals that of Zeldris'. His aura is so powerful that it completely terrifies the human souls inside Excalibur. Merlin has stated that Cusack is a monster whose power far surpasses the Ten Commandments, and alongside Chandler, he is the oldest and strongest demon in the Demon Realm excluding the Demon King himself. Even Zeldris claims that Cusack is stronger than him, with Cusack himself stating that Zeldris will one day surpass him.

Like all members of the Demon Clan, Cusack is able to manipulate the mysterious jet-black power of darkness for a variety of purposes, such as forming wings for flight and regeneration.

Cusack possesses immense levels of endurance, as shown when he remains mostly unfazed from having been pierced through the abdomen by Meliodas’ darkness in his Assault Mode, though he was immobilized until the former recalled it back. He also possesses immense physical strength, being able to completely shatter a stone wall with a single grip and easily breaks free from Merlin's Icicle Castle just by moving.

In his true form, Cusack is more powerful than ever. He has shown the ability to shoot energy beams from his eyes that can cause massive damage. He is capable of fighting evenly with Ludociel, leader of the Four Archangles, even gaining the upper hand. In this form, Cusack possesses immense levels of durabilty as he remains completely unscathed after being hit at point-blank range by Merlin's Double Impact spell and Ludociel's Grace. Even after taking a powerful Ark imbued jab from Ludociel, Cusack remains unharmed. He also possesses immense speed and reflexes, as shown when he moves in between Zeldris and Ludociel in an instant to stop the latters attack, and is able to keep up with the speed of Ludociel's Flash. Despite having his original magic power sealed, excluding the Demon King, Cusack is celebrated amongst the Demon Clan as the absolute strongest demon who is strong without equal, fast without compare, and tougher than any other.

Abilities

 * This ability allows Cusack to link with someone through eyesight. When activated, his eye and the eye of his target glow the same color and the person does the same movements as Cusack.

Weapons

 *  Dual Sword Hilts: Cusack carries two identical sword hilts on both sides of his hips, which he channels his darkness through to create two blades. He is extremely skilled in swordsmanship and is the one who taught Zeldris how to use a sword.

Power Level
Cusack's power level in his True Form are as follows:

Zeldris
Cusack strives to impress Zeldris in any sort of way and admires him, calling him the most worthy of being the Demon King. He is also envious when Zeldris praises someone else as he said that if his love for Zeldris was on the line then he would not lose to anyone. While not conducting any missions, Cusack is shown to attend to Zeldris like a butler and is shown to be comically wounded when he denounces his tea and advice as terrible. He also displays complete rage when Meliodas brought Zeldris down with his darkness and was ready to attack Meliodas for it, and he shows great respect toward him and belives that Zeldris will be the one to surpass him.

Chandler
Cusack seems to get along well with Chandler as they talk and walk casually together. However, Cusack does seem to get annoyed at Chandler whenever Meliodas is mentioned, as it upsets the latter and he becomes a cry baby and obsesses over Meliodas.

Prelude to the New Holy War arc

 * Arthur Pendragon vs. Meliodas, Zeldris, Cusack & Chandler: Win

New Holy War arc

 * Assault Force vs. Zeldris, Chandler & Cusack:

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