Tristan Liones/Plot

Epilogue arc
On his tenth birthday, Tristan heard one of the maids talk about the Seven Deadly Sins meeting in the castle that same night. Ignoring the truth about them and only knowing that they were criminals who were once exiled from the kingdom, Tristan assumes that they intend to take control of Liones. He then runs off to call other children of the kingdom telling them that as a Holy Knight who protects the peace of Liones it is his duty to capture them.

When his friends do not take any of his words seriously, Tristan decides to go to the castle and ambush them on his own. There, he is surprised by Elizabeth who was looking for him, which worries Tristan for having been discovered by the Sins. Meliodas and the Sins introduce themselves but, although everyone is friendly with him, Tristan is suspicious stating that he knows they intend to do a coup d'etat. Everyone takes it as him trying to play hero, even Meliodas jokes about acting like a villain to falsely prove his son's suspicion.

Tristan is then taken outside where the entire kingdom has gathered to celebrate his birthday. Although Tristan insists that his father is the leader of some villains, Ban tells him that if so, the people of the kingdom would not admire him the way they do. Tristan sticks to his ideas by highlighting all of his father's bad habits. Gowther then uses his powers to give him a special gift: to show him the true story of the Seven Deadly Sins.

The next day, Tristan goes to a picnic with his parents. After a sword training session with Meliodas, he tells him that his future expands like heaven and that he does not have to become a king, which may be what he decides, even a Holy Knight. Tristan then says that he has already decided: he will be one of the Seven Deadly Sins.

Grudge of Edinburgh
After having a nightmare about a time in wich he injured Lancelot during a training after losing control of his demon powers, Tristan spends the day learning to ride with Gowther while stopping to heal some injured citizens with his Goddess power. At dinner he has an argument with Meliodas for neglecting his training in favor of learning other things like herbology from Hendrickson leading Tristan to deny wanting to be what he did as a child and that his father is not able to understand him. A conversation with his mother clarifies that he can be a Holy Knight who helps people and not just fight, although there may come a time when he has to simply fight to protect others.

The next day, Tristan finds out that his mother has been cursed and Hendrickson is unable to help her. Hearing that only a Goddess could break the curse, Tristan decides to try, discovering the identity of the one cursing his mother. Despite failing to stop the curse, Tristan finds the location of the perpetrator and sets out there. On the way, he finds a group of giants and fairies being attacked by an Empty. Tristan fights and defeats it, but gets upset when one the fairies kills it when this one was about to ambush him, but is later revealed that the Empty was never alive since it was a mere puppet. Upon hearing that many giants and fairies have been kidnapped and taken to the place he is going, Tristan decides to go along his new friends to rescue them.

The mysterious fairy explains that they are leading to Edinburgh, a fallen kingdom only inhabited by its king, Deathpierce. Upon arrival they are attacked by an army of Empties and by Deathpierce's subordinate creatures, Knight and Mage, sent by the one who cursed Elizabeth, Priest. Tristan manages to face the Empties but is outmatched by Knight as he is inhibited from unleashing his demonic power. This leads the fairy to kill the creature to save him, revealing himself to actually be Lancelot.

Chaos in Liones arc
Tristan appears on the streets of Liones where his three followers, the Tristan Platoon, were attacking Percival's group whom they believed to be Knights of Camelot. Recognizing the Dragon Handle that had already been reported in an ally's possession, Tristan orders Chion to remove his spirit's spells from the boy, but then Percival mummifies Chion's arm and attacks Jade, for which Tristan sends him flying with a kick and after taking flight with Goddess wings, he asks Percival who he really is. Hearing him speak in a strange language, Tristan attacks him with Twinkle Star, but to no effect, leading him to confirm that Percival is not a demon. Tristan then knocks Percival down with his swords, but his three friends rise to shield Percival and leave everyone shocked when they manage to bring Percival back to his senses.

Tristan uses his magic to heal Percival's friends, but is unable to reverse the mummification of Chion's arm. He suggests going to Hendrickson or his mother to figure it out, until Percival manages to heal him himself. Tristan then asks Isolde what led to the situation, but the girl is embarrassed that she "had her chastity taken from her" and she leaves in tears. Tristan formally introduces himself to Percival, revealing himself as the prince of Liones and one of the Four Knights of the Apocalypse as Percival. Tristan is glad that the four of them are in Liones, revealing Lancelot to be one as well.

When Lancelot arrives, Tristan is glad to see him and asks if he already met the fourth member he brought, to which Lancelot informs that the fourth member had fled the scene. Tristan asks why he ran away, to which Lancelot says he does not know and that the king charged everyone to "clean up the prince's mess". Lancelot orders Tristan's party and Percival's party to check the east and west gates while he himself checks the south gate. He also asks Tristan to tell them everything he knows about the fourth member. Tristan reveals to them that his name is Gawain and that he wears armor and has golden magic, despite knowing nothing else since he never took off his armor during their first meeting and the trip. Lancelot inquires upon what else Tristan is hiding, something Tristan initially denies, though seeing Lancelot read his mind, he reveals that Gawain is a blood relative of King Arthur. Although Tristan is alarmed that this information will wreak havoc between them, Lancelot says that it is better to know in advance.

While searching for Gawain in the east gate area, Tristan defends Percival and Lancelot from Chion's criticism and distrust. Even so, after finding Chion trying to bury alive who he thinks is Gawain, Tristan stops him with a Twinkle Star and reveals that guy is not Gawain but an apprentice who found the latter's armor.

Tristan arrives at the site where Gawain and Percival were fighting Pellegarde by following Gawain's magic. Tristan berates Gawain for disobeying his orders to wait for him. When Percival tells him that Pellegarde is a knight from Camelot, Tristan manifests his demon and goddess powers, leading Pellegarde to deduce that he is the one with "light and dark in his eyes" of the Four Knights of the Apocalypse.

As everyone share different opinions about what to do with Pellegarde, with Tristan suggesting take him prisoner, Percival deciding to talk to him, they give the Camelot knight the opportunity to kidnap the latter, leaving the rest trapped in a Perfect Cube. Tristan berates Lancelot for not using his magic to stop him, to which Lancelot points out that he would have harmed Percival as well. After Gawain uses Absolute Cancel to nullify the Perfect Cube, Tristan takes flight to go help Percival.

Tristan comes to Percival's aid after Percival is beaten by an upset Gawain for his interference in Pellegarde's death. While healing Percival, Tristan berates Gawain for attacking a comrade, but Gawain denies being on the same level as them and that he never intended them to become friends, provoking Tristan to attack her, but the prince refuses to raise his swords against an ally. Gawain simply shoves him out of the way by calling him a wimp and when Percival gets upset with Gawain, Tristan tells him not to piss her off anymore. However, Pellegarde intervenes and Tristan watches in amazement as he overpowers Gawain. When Pellegarde decides to retreat after a tantrum from Gawain, Tristan allows him to, having saved Percival and not wanting to fight a wounded man, but warns him that he will not do it again. Tristan then comforts Gawain for her defeat by praising her and assuring her that she will win the next one, which brings her spirits back to her.

Tristan feels a strong demonic magic in Liones, so Gawain teleports him and Percival back to the kingdom. Confronting a resurrected Galand and Melascula, both recognize Tristan's mixed magic by its simlarity with Meliodas' and Elizabeth's.

Upon evading Galand's attack, Tristan is surprised by Melascula who traps him in Meian no Ori. However, Tristan breaks free enchanting his sword with Ark, claiming that she will never defeat them. He warns Melascula that she should surrender as Galand has already been defeated, but Melascula creates a creature of demon and goddess souls, rendering it immune to Tristan's Ark. Melascula talks about the repulsiveness of Tristan being a Nephilim, though she sees that in appearance and magic he is more like his mother though nowhere near her in power. Tristan happily agrees with her statement and asks her to tell him about when his mother was called "Bloodstained Ellie". Melascula recoils surprised by his attitude, noting that Tristan does not resembles his father, to which the boy agrees as well.

When Lancelot tricks Melascula into assuming her giant snake form, Tristan is forced to unleash his demonic power to finish her off. Melascula then says that Tristan is actually a monster like his father, to which Tristan says that it is why he does not like using that power.

As Percival shows amazement at Tristan's power and Gawain accuses that Tristan hid that power from her, Tristan says that it is more inconvenient than what it looks like. While Percival's friends and the other Holy Knights gather to celebrate the Four Knights of Apocalypse, Melascula and Galand reappear as having fused into a being called Melagaland. Tristan says that they must just defeat them again, but none of his attacks have any effect on them, making him realize that they are a completely different being now. Tristan then uses his Falling Stars, but for some reason, all the shots miss the target. After Gawain uses her Sunshine Burst, Tristan tries to take Percival out of Melagaland's reach, although Donny also uses his Telekinesis to push Melagaland away. Seeing Melagaland hurt by Gawain's attack, Tristan and Percival try to charge into it, but inadvertently crash into each other, knocking each other out.

Tristan is carried away from the battle by Nasiens and Hendrickson, and after being healed by the latter, Tristan saves Isolde from being crushed by Melagaland stating that the girl always pushes herself for his sake. After evading Melagaland's attack to leave Isolde with Hendrickson, asking him to also call for Lancelot, Tristan soon overcomes Melagaland with his demonic power, managing to rip its face off and pierce its body with darkness. Melagaland then invokes the Meifu no Bansan, but Tristan removes the technique without issue and proceeds to rip off Melagaland's snake head despite saying that he agrees to the plea to stop, stating that he is unable to control himself in that state. Tristan eventually wipes out the rest of Melagaland with his swords. Percival tries to tell him that he can switch back now, but Tristan states that he can't do that so easily.

When Arthur Pendragon descends into the battlefield from the sky on a staircase made of debris and congratulates Tristan for his fight, Tristan flies to attack him, to which Arthur says that he will be the first one he will test. Arthur manages to repel Tristan and send him flying away, claiming that his demon blood makes him into a bloodthirsty beast. Tristan manages to pull himself together to attack Arthur with his darkness, stating that the manipulative speech he was giving the kingdom is making him vomit. Arthur says that Tristan is still young and attacks him with a magic blast, but Meliodas appears to rebound the attack with Full Counter.

When Tristan says that they are wasting time and that he will take Arthur down himself, Meliodas orders him to stay out before jumping at Arthur and starting a fierce sword fight that causes surrounding impact strong enough to blast a mountain to pieces. Tristan suddenly tries to interfere, telling his father to shut up when he asks him to withdraw. As Arthur says that he should not speak to his kind father like that, Meliodas saves Tristan from being beheaded by Arthur and then attacks the king with Trillion Dark to finally send him flying away with a kick.

Meliodas asks his son if he is hurt, leading Tristan to angrily reject his help and state that he could fight with his own power even when Meliodas tries to make him calm his mind down. Arthur says that Tristan does not understand a thing and that he is only dragging his father down since, hadn't it been for the boy, Meliodas would not have been hurt and Arthur would have been hurt far worse. Arthur also tells Meliodas that he should not be worried about his son in the middle of an national affair like that, but Meliodas says that if he does not worry about his son then he can not be considered a king. Arthur asks Meliodas what is needed to be the king of a country, affirming that it is resolve and action strong enough to cast their individuallity and feelings aside for your people's sake, even if it is detrimental to your beloved son and wife.

As Tristan begins to completely lose control of his demon side, Meliodas runs to help, receiving an attack from behind from Arthur who tells him to die protecting his beloved son.

After Lancelot stops Arthur's attack, Tristan breaks free and begins to wreak havoc over the place, forcing Lancelot to stop him with his Shining Road. Meliodas takes care of Tristan who returns to his senses to see Lancelot fight Arthur, reproaching his father for commenting that Lancelot inherited his father's skill to tease people. As everyone gets surprised when Lancelot manages to overwhelm Arthur, Tristan tells Percival that it is only natural given that, despite having been evenly matched until his disappearance three years ago, Lancelot's power now far surpasses him and even rivals that of the Seven Deadly Sins. Tristan urges Lancelot to finish the battle until the Knights of Camelot appear and convince Arthur to stand down, who, before leaving, declares war against the Four Knights of the Apocalypse.

The night after the battle, Tristan is training with his swords remembering with frustration the trust that Meliodas had shown Lancelot and not him.

Wallnack arc
The next morning, Tristan participates in the meeting in the war room to discuss the situation with Camelot. When Anghalhad asks why they are fighting a kingdom destroyed 16 years before, Thetis explains that Camelot was recreated in an alternate dimension by the power of Chaos but is now starting this war because there is a price to pay in order to rebuild and maintain the new Camelot. To further strengthen her statement, she uses her magic to teleport everyone to a landscape that had been stripped of various parts, leaving only empty spaces. Meliodas explains that it is the result of Arthur creating a new Camelot, to wich Tristan asks from whom he got that information, to wich Meliodas reveals that he heard from Percival's grandfather, a former Holy Knight of Camelot. When Percival and Donny ask why Meliodas didn't go to Camelot himself when he could, Meliodas replies that he couldn't because he is a demon, leading Thetis to explain that Camelot is protected by a barrier that prevents any race except humans from entering. As Meliodas says that they entrust everything to the Four Knights of the Apocalypse for being humans and half-humans, Thetis says that it is normal that Camelot's barrier does not affect half-humans since it has never been heard of beings born from two different races and also that it would reduce the defensive capacity of the barrier. When Tristan interrupts her to point out that they're at a dead end by not being able to go to Camelot, Thetis and the rest can't come up with a solution, leading Percival to suggest they just go on an adventure to find one.

As they walk through the kingdom, Isolde asks Tristan if he's better now, to which he tells her that he's still in pain even though his wounds are healed. Isolde reproaches him that he was so careless because of her and that the Tristan Platoon should protect him and not let him risk his life for them. Tristan thanks her for her intention but tells her that as partners, none is more important than the other, saying that he always wanted to be like the legendary Seven Deadly Sins next to them. Isolde kneels before him thinking that as long as she can give her life for Tristan, she doesn't care that he doesn't see her as more than her friend or companion. Tristan then gives her a new ribbon to replace the one that was destroyed, which Isolde gladly receives. Gawain, who was being ignored in the whole situation, decides to leave saying that they can talk about love and lose theirchastity, leaving Tristan confused.

Tristan and the rest of the Tristan Platoon meet the Percival Platoon, all with their new outfits. Tristan comments that Lancelot obviously didn't get new clothes since he is the only one who came out intact from the last battle and that his actual clothes are really precious to him, since the Fairy King made them.

On the day everyone is finally setting off in search of an entryway to Camelot, Meliodas divides the Four Knights into search teams. The Tristan Platoon is assigned to go to the old Camelot. Tristan then explains to Percival who is Dubs and how Lancelot had been searching him to get a weapon that could resist his magic power.

Before leaving, Tristan has a farewell moment with his parents, being loving towards his mother and awkward with his father. He then gets angry when Lancelot says that he calls them "mom" and "dad" instead of "mother" and "father".

As all the teams go together and reach the city of Wallnack, Tristan explains that the city is a relay point between Liones and Dalmary, and the huge walls surrounding it are a protection against the constant attacks from bandits and war criminals. Lancelot is annoyed with Tristan for getting carried away with everyone's wishes to enjoy the local festival and urges him to find an inn. Already at the inn, the boys decide to divide the rooms with a game of rock, paper and scissors. In the end, Tristan ends up having to share a room for two with a stranger. There, he is greeted by a mysterious, barely clothed woman who calls them a prince. She is delighted with her presence, although she downplays it by not wearing her clothes, so Tristan decides to help her even though he can not button her shirt properly. When Isolde bursts in breaking down the door, she dress Ioladio herself. The woman asks Tristan to go to the village festival together, since she wants to talk to him about something in private, revealing that she is aware that he is one of the Four Knights of Apocalypse.

At the festival, Tristan says that he already felt something strange when she called him a prince upon seeing him, suggesting that she came from Camelot. She introduces herself as Ioladio and tells Tristan that this festival used to be held in commemoration of those who died in the attacks that Liones suffered, but Tristan agrees that now it is held to commemorate those who died during the Holy War 16 years ago. Ioladio says how beautiful that tradition is, something that would never be found in her homeland, and that for now they should pray together. When the magic that was affecting the entire town is momentarily lifted, Ioladio reveals that his Jamming power will continue to prevent all magic detection within Wallnack, so none of his allies can find Tristan. Seeking to answer his earlier doubt, Ioladio denies being Camelot's ally but reveals that she is not human, reverting to her original demon form.

Ioladio suddenly attacks Tristan, with this one dodging and responding with his Ark-enchanted sword. As Ioladio is able to avoid his strikes, Tristan ask her abour her motives to attack him, even if it is because he is a descendant of the Goddess Clan or the son of a traitor from the Demon Clan. Ioladio neglects his words and shoots and elastic adhesive that binds Tristan to the ground, coming then to beat him up using the rebound to harm him more. Tristan finally breaks her adhesive with his bare hands and lands a good punch at Ioladio to stop her down. Tristan begins to talk about how the demons suffered the same losses as the other races during the Holy War and Ioladio reveals that she was sent by Arthur Pendragon to eliminate the Four Knights to avoid being killed by her own comrades whom Arthur brainwashed. Tristan asks why she did not tell him sooner, to which Ioladio replies that she is not afraid of dying since she and her companions would be killed by Arthur eventually, but she wanted to at least find out if the Four Knights were strong enough to be a threat against Arthur. Having confirmed this, she asks him to defeat Arthur, though Tristan says that they all need to work together and that his own teammates are skilled enough to take on hers.

Tristan rushes upon seeing Chion's Shichoso in the sky, but when he arrives to join his companions, he discovers that Jade has been killed in battle.