Monspeet/Plot

Albion arc
After Hendrickson manages to partially remove the seal that bound the demons for the past 3,000 years, Monspeet and the rest of the Ten Commandments appear before the terrified former Great Holy Knight. After being informed by Fraudrin of the current events in Britannia, Zeldris suggested that they should head to Edinburgh Hill in order to recuperate their severely drained magical powers, which everyone agreed on. They left Zhuhur Valley by flight, leaving behind a terrified Hendrickson. Arriving at Edinburgh Hill, Monspeet and his fellow Ten Commandments find a castle in ruins and conclude that a great magical power imploded within the castle, causing its the destruction. They also come across the remains of Danafor and link the kingdom's disappearing to Meliodas.

Resting in the remains of Edinburgh as they began recovering their magic power, Monspeet and his comrades discuss the recent awakening of two Albions from the north and the south and witnesses Galand heading to the latter direction. After Galand returns victoriously, the demons sense Diane heading towards them and Galand, still willing to fight, heads towards her location along with Monspeet. Both of them overpower Diane until Monspeet is sent flying by Matrona. After recovering from Matrona's surprise attack he suddenly senses the several fairly strong presences coming towards them, one of which suspiciously similar to Meliodas. In order to determine if it's really Meliodas, he fires a Gokuencho towards them, which burns down a forest and plows through a mountain, only to be stumped when he suddenly can't sense his attack anymore. He questions whether Meliodas used Counter Vanish only to deduce that something must have swallowed. it. He laments for a moment that he wasted all the magic he recovered from eating human souls on that move but accepts the loss shortly after.

Istar arc
As the Commandments continue to gather souls to restore their magic, Monspeet, along with the other Ten Commandments, is surprised when Meliodas suddenly appears before them, easily defeats Galand, and warns them if they wish to continue the war that ended 3,000 years ago, they will be crushed. In response, Zeldris orders that they spread out to take over Britannia. He and Derieri then leave and arrive at the town of Bellford.

Great Fight Festival arc
He and Derieri continue their purge in the north of Britannia, having devoured the souls of nearly every person in nine cities and villages and showing no signs of stopping.

Later on he, along with the other Commandments, arrives to aid Drole and Gloxinia, who are facing off against Meliodas. He watches as Derieri and Meliodas exchange blows and explains Derieri's power. After catching Meliodas, he flies him into the sky, noting that with his arms broken he should not be able to use Full Counter anymore. He uses Gokuencho on Meliodas but is surprised when he comes flying out of the dust cloud and nearly takes his head off. He commends him on the effort while sealing his wound, and becomes embarrassed by a remark Derieri makes about the scene. After Meliodas bears more attacks from the Commandments, he prepares to unleash his Revenge Counter to annihilate all of the demons at once. However, Estarossa easily blocks his brother's attack and kills him, although Melascula dies to Ban in the process as a last effort by Fox's Sin of Greed to save his friend.

Defensive Battle for Liones arc
Monspeet and the rest of the Ten Commandments continued to take control of Britannia and eventually invaded Liones. There, Monspeet remains at the margin at the beginning, watching with astonishment the power of Escanor in his fight against Estarossa. Finally, he and Derieri decide to take over the disabled Holy Knights and take the Liones Castle. Then, Denzel arrives, announcing to protect the kingdom by killing the demons, and allows the goddess Nerobasta to use his body as a vessel in order to fight the Commandments. Monspeet mentions the Ark's ability of the Goddess Clan, capable of counteracting the darkness of the demons. When Derieri manages to easily assassinate Nerobasta, Monspeet asserts that things would have been different had they inflicted one of the Four Archangels. Thus, both Commandments declare complete the taking of the castle.

While Fraudrin and Grayroad were concerned with the capture of the castle and the remaining Holy Knights, Monspeet took a moment in the city to fix Derieri's hair. Then, both of them noticed a strange disturbance and went to see what it is. When they arrive, they find a giant pig causing havoc, being ridden by some unusual travelers. Monspeet manages to intimidate Zaratras with his presence, warning him not to act. However, he is surprised when Elizabeth manages to use Ark to destroy Derieri's hand. When this last one is sent to fly by a revived Meliodas, Monspeet leaves immediately to look for her. When he finds her weakened in the forest, Monspeet asserts that no one could have been responsible in addition to Meliodas, despite the fact that they had witnessed his death. When Derieri decides to fight again, Monspeet orders all the nearby demons to sacrifice themselves to charge Derieri's Combo Star. While this last fight, Monspeet attacked by surprise with his Kaijinryuu. However, Meliodas reflects his attack with his Full Counter, resulting in both Commandments being consumed by the rebound.

Prelude to the New Holy War arc
When Zeldris calls telepathically to the other members of the Ten Commandments, Derieri and Monspeet reveal themselves to be alive. However, both decide not to respond to Zeldris, as they have decided to stand by the side of the battle and stay in a peaceful life in the hut of humans who had given them asylum after they got rid of a bear that caused disasters on their farmland. Derieri asks Monspeet if he really is fine with that kind of life and calls him weird when says that is fine because there is nothing that makes him worry about her. There, they both discuss the reason Meliodas forgave their lives, as Elizabeth had done 3,000 years ago.

When the farmland girl comes with some food and drink, Monspeet gave his thanks as the girl thanks for what they both do for their farmland.

New Holy War arc
Sometime later, after the new Holy War began, Monspeet is still with Derieri residing in the human village. While relaxing there, they notice that war broke out, but they decide to not intervine. Monspeet tells Derieri he would rather live peacefully with her, but if Zeldris finds them they will be punished, and the village as well. Derieri gets up and tells Monspeet that she is going to surrender her Commandment to Zeldris, as the mark in her cheek fades away.

In that moment, the lady who sheltered them comes to warn them about the conflict, when she suddenly is burned to death, shocking Monspeet and Derieri. Estarossa enters and teases them about playing house. Derieri, enraged, attacks him, but is quickly dealt with. Estarossa then takes out the soul of the girl's corpse to eat it, but Monspeet prevent it, switching it for an apple by using his innate magic.

Estarossa then attacks Monspeet with a series of punches, managing to put him into a head lock. Estarossa states that he has come to collect their Commandments, even if he has to kill them for that. Derieri tells him to stop, that she already was going to give up her Commandment. Monspeet tells her that he was going to as well, because if he would be released from the "silence" of his Commandment, he could finally tells her about his true feelings.

Estarossa reveals that he want to take all Commandments for himself. Monspeet remarks that he is twisted and that he knows something that every Commandment know except for him. Suddenly they swap places, wiht Monspeet now choking Estarossa. Monspeet reveals that he was waiting Estarossa to have him completely immobilized, to use a technique called Conjurer Joke, that let him swap any two objects with similar size or mass, including himself.

Monspeet continues with his story, revealing that Estarossa was born without the power of darkness, and that the Demon King gave him a Commandment out of pity. Monspeet tells Estarossa that if he takes any more Commandments other than his own he will die, due to the fact that having one Commandment was already eating away his soul and mind. Estarossa tries to get free with his Hellblaze, but this has no effect in Monspeet and eventually is driven unconscious by him.

Thinking that they had won, Derieri walks up to Estarossa and Monspeet, asking what they should do with him. Monspeet warns for Derieri to step away but too late. Estarossa grabs her by the neck intending to pierce Derieri, but Monspeet uses Conjurer Joke one last time, switching himself with Derieri, and having his last heart ripped out instead.

After his heart was crushed, Monspeet sends Derieri to fly away from the remains of the cabin. With his last strength, Monspeet takes the face of Estarossa, and after lamenting in the end not having been able to tell Derieri those words that he kept hidden in his heart, he releases a Hellblaze that engulfs both him and Estarossa.