In Heavy Lies the Crown, a chipped Ilian is first seen in a flashback where A.L.I.E. entices him to kill his father and brother and fatally torture his mother in an attempt to force the latter into accepting the chip. His mother, remaining intransigent, continues to refuse, believing a demon has occupied Ilian's body. As Ilian is about to cut his own throat from A.L.I.E.'s advice, she is destroyed by Clarke in the City of Light and Ilian is freed from her oppression. Freeing his dying mother from her bonds, he mourns as she asks to be avenged and dies in his arms.
Ilian makes his way to Polis where he is next seen discussing his need for revenge against Skaikru (who he blames for the death of his family) with Trishanakru's ambassador Rafel. The ambassador tells him of his plan to kill King Roan in single combat as he is protecting Skaikru. Ilian at first does not wish to harm the king as he has no quarrel with him, but soon agrees with Rafel that with the king dead Trishanakru can seize power and then destroy Skaikru.
Later, while Ilian and Rafel are further discussing their plan they are approached by Marcus Kane and Octavia who attempt to dissuade them from going through with their plot to challenge Roan. Ilian and Rafel, both seething with hatred for the Sky People, blatantly refuse to back down from challenging Roan to single combat.
Ilian attends the meeting of the ambassadors and the king and appears slightly shocked and angered upon hearing about Rafel's death. Ilian immediately suspects (correctly) that Rafel was assassinated by Octavia and asks her if she plans on killing him too. Octavia denies knowing what he's talking about and then gives her sympathy regarding the death of Ilian's family.
In The Four Horsemen, Ilian and his people are looting and destroying all the technology in Polis that they can find. When Terro, one of the looters, intercepts and threatens Octavia as she is following the flamekeeper Gaia, Ilian steps in to prevent them from fighting, telling Terro that they are there for the tech, nothing more. When Octavia asks him why they're destroying technology, Ilian replies that it is because that is what A.L.I.E. used to control them, and they'll never let that happen again. After Octavia leaves, Ilian orders one of his people to follow her.
Ilian and his followers having tracked Octavia to the Flamekeeper's temple and realising there is probably tech there, break inside. They find Octavia, Gaia and Indra, and Ilian orders the trio to drop their weapons, which they do so. Upon searching Gaia's pack, Ilian finds what he believes to be the Flame. "For my mother", he says, then duly smashes it with a hammer. He and his looters then trash the temple and leave.
In The Tinder Box, Ilian discovers Octavia, badly wounded and barely conscious in the woods near to Arkadia. Ilian carries Octavia to Arkadia and claims that he was on his way home from Polis when he found her (which may or may not be true). While everyone is distracted tending to Octavia, Ilian slips away and makes his way through Alpha Station.
Ilian finds a load of flammable liquids and a cart to carry them. He follows the electrical cables to their source.
Once inside the server room, Ilian makes his preparations. Octavia and Niylah find him just as he is about to set the station ablaze. Being too weak from her wounds to stop Ilian physically, Octavia attempts to talk him down. However, Ilian is not deterred and drops his blazing torch on the flammable liquids he has poured on the floor. The initial explosion almost kills both Octavia and Niylah, but they were able to get out of the room in time. Ilian helps the pair outside and then continues to watch as the flames engulf the entire station.
In We Will Rise, it is revealed that although much of Alpha station was burnt, a lot of it is still inhabitable and Ilian has been imprisoned in a cell. While Ilian is contemplating his situation, a mob of angry Arkers, furious at Ilian for his arson, break into the cell with the intention of killing him. Ilian attempts to fight them off but is quickly overwhelmed and beaten to the ground. He is only saved by the arrival of Kane and some guards who disperse the mob and take Ilian to the infirmary.
Ilian has his injuries tended to, but is restrained to his hospital bed. Eventually, Ilian and Octavia are the only ones left in the med bay and Ilian tells Octavia that he’s glad she survived. Octavia warns Ilian that he will be killed soon as, “blood must have blood”. Ilian states that he didn’t kill anyone in the fire, but Octavia scornfully tells him he has caused the eventual death of everyone by compromising the station and that the Sky People will kill him in revenge. Ilian says that he didn’t know about the apocalypse event when he lit the fire and that he never meant to harm anyone. “The sword doesn’t care what you meant”, replies Octavia, “it just cuts”.
Later on, Kane, David Miller, Monty and some guards abruptly arrive in the infirmary and lock it down, just moments before a mob arrives outside the doors demanding Ilian be turned over to them. Miller questions Kane’s decision to protect Ilian, reminding him that they would have floated Ilian if they were on the Ark, but Kane declares that “mob rule” will not dictate justice in Arkadia. Monty is steadfastly aligned with Kane’s views, saying that the mob will kill Ilian if they let them through the doors. Ilian remains silent. Kane pulls out a pistol and loads it, determined to protect Ilian even if it means killing one of his own people, saying: “if we let them descend into darkness, there’s no coming back”. Octavia tells Kane it’s the end of the world and darkness is all that is left – she then suddenly heads over to the door and unlocks it before Monty or Kane can stop her. The mob rush in and while Kane tries to hold them at gunpoint, Miller stuns him in the back with a shock baton, saying he’s sorry. The Arkadians advance on Ilian but before they grab him Octavia asks that she be the one to kill him.
Ilian is manhandled outside and put on his knees in the mud before Octavia. Monty begs Octavia not to go through with the execution, telling her she’s not a murderer, but Octavia says he’s wrong and puts her gun to Ilian’s head. Ilian, his face badly beaten, stares stoically up at Octavia and tells her to get it over with. Octavia hesitates as the crowd looks on silently. Suddenly, the warning alarm sounds signalling the arrival of black rain and most of the crowd rush inside to safety. Octavia continues to point her gun at Ilian, but Kane is able to convince her to drop her weapon after he reminds her of how Pike executed Lincoln in the same way. A distraught Octavia, runs out of the gates of Arkadia, while Jaha cuts Ilian’s bonds and tells him to run. Ilian looks back at his saviours as if he is about to say something, but then flees from Arkadia.
In Gimme Shelter, Ilian tracks Octavia through the forest and eventually spots her horse, Helios, apparently abandoned. As Ilian approaches Helios, Octavia comes up behind him and holds a knife to his throat, demanding to know why he is following her. Ilian tells Octavia that she won’t survive on her own and says he wants to help her because of how she spared his life in Arkadia. Octavia refuses his help and mounts her horse, but at that moment a storm begins, unleashing black rain which burns skin on contact. Ilian is unaware of just how dangerous the rain can be and calls it strange, but Octavia urges him to climb on Helios with her and the pair ride off in search of shelter.
Finding a cave, the duo rush inside and strip off their contaminated clothing. Fortunately, there is a pool of fresh water in the cave with which Ilian and Octavia are able to wash themselves. Ilian asks what the black rain means; Octavia replies bluntly that it means they are stuck inside the cave until the rain passes and that she doesn’t want him to talk to her. Octavia goes to wash off Helios and suggests that Ilian should light a fire, “you’re good at that”, she says with disdain.
While waiting around the fire for the storm to pass, Ilian finally breaks the awkward silence by asking Octavia where she will go. When Octavia doesn’t answer, Ilian goes on to tell her that he doesn’t know where he’s going either, because if he returns home to his farm, it will remind him too much of his family and what he did to them while under A.L.I.E.’s control. Octavia remarks that Ilian is not a murderer because he feels the pain of killing, whereas she feels nothing. She tells him he should go home to his “stupid sheep”. Ilian doesn’t believe that Octavia is a heartless killer, recalling that he saw the pain in her face when she was about to execute him. He claims that she doesn’t want to feel the pain of taking a life but that it’s still there. Octavia angrily tells him to shut up, but Ilian continues talking, asking Octavia how she became the person she is and saying he believes that deep down, she is still the person she was before. Octavia tells him he’s wrong, and then in a moment of madness and depression she walks towards the entrance of the cave with the intention of letting the black rain kill her. Ilian prevents her attempted suicide and wrestles her back inside the cave, holding her to the ground. Suddenly, Octavia kisses a surprised Ilian, and begs him to, “just let me feel something else” and the pair then has sex.
Once the storm passes, Ilian informs Octavia that he has decided he is going home, “back to my stupid sheep”, and tells her how to find his farm. Ilian leaves, but Octavia catches up with him on her horse, telling him to get on and that she’ll take him home.
In DNR, Ilian is sowing crops on his family’s farm while Octavia is trying to till the ground. “Are you tilling the soil or stabbing it?” Ilian jests. Octavia tells him she believes planting crops is pointless as they’ll both be killed by Praimfaya before anything grows. Being less pessimistic, Ilian points out that people have survived such a fate before and that they are planting crops for the sake of any survivors. Octavia continues to struggle to use the plough, so Ilian steps over to show her how it’s done but is interrupted by a fellow Trishanakru clan member, Ankara, who has come to visit him. Ilian warns Octavia that his people are wary of strangers and that she should keep a low profile before going to meet his visitor. Ankara informs Ilian that Trishanakru are preparing for war and going to assist Trikru and their allies in pushing Azgeda out of Polis, implying that Ilian should accompany their force as he is one of their warriors. Ilian declines to leave his farm which prompts an angry outburst from Ankara – “your mother would want you to fight!” she scowls. Ilian orders Ankara to leave his property and after she departs, Ilian is approached by Octavia who is surprised to learn that he is a warrior. Ilian simply tells her that it’s not much fun fighting at the end of the world.
Later, Ilian lies in bed with Octavia when she tells him that she can’t stop thinking about the war going on and the fact that she isn’t in it. Ilian states that no war will stop Praimfaya, but Octavia replies that she would prefer to die a warrior’s death instead of “melting”. Ilian quotes a saying his people say which infers that death is not the end and that when someone dies, they will be reincarnated. When Octavia asks him whether or not he believes the saying, Ilian recalls the cycle of crops and how when they die off in winter, they return in spring: “most people don’t know when their winter will come”, he states, “but we do, and that’s a gift. Why waste it on fighting?”
Ilian takes a walk somewhere on his farm and upon returning to his house he finds that Ankara has come back with two of her warriors – all three of whom, having been butchered by Octavia, are now lying dead in his field. A bloodied Octavia approaches Ilian and tells him remorselessly that, “this is who I am”. Ilian, realising that the Trishanakru warriors must have provoked Octavia in some way, is shocked at what has happened and stares at their bodies while Octavia leaves.
In Die All, Die Merrily, Ilian learns of the nuclear bunker that has been found in Polis and the Final Conclave which is being fought for its possession. Being a skilled warrior, Ilian is chosen as Trishanakru’s champion and arrives in the capital to receive his clan’s sigil from Gaia before taking a position on the podium next to Octavia – who has been declared Skaikru’s champion. Octavia asks Ilian what he’s trying to prove and Ilian replies that he’s there for his clan, not for her, he then listens to Gaia’s announcement. Gaia states that the battle to the death will be fought by the champions within the walls of Polis until only one warrior remains: that champion’s clan will then claim the bunker, while the other clans will perish in Praimfaya. As the ceremony is ending however, Luna, who is the last member of the Floukru clan arrives and claims the position of the 13th champion. When Luna is asked who she is fighting for considering all the members of her clan are dead, everyone at the ceremony is shocked when she announces that if she wins then she will let no one will claim the bunker and everyone will be left to die in the nuclear apocalypse.
In the armoury, Ilian arms himself with a halberd and rehearses his moves. When the conclave is about to begin, Ilian and all the other participants are led out into the city to their separate starting positions. A horn is then blown from the Polis tower to signal the commencement of the conclave.
Sometime into the conclave, Ilian enters a house to find Octavia tending to a small cut on her arm. Ilian immediately shows Octavia that he means her no harm and proposes that they enter into an alliance together as several other clans are doing. Octavia rejects his proposal, saying she doesn’t need his help, and tells him he should have stayed back at his farm. “Octavia, I won’t be your enemy”, Ilian replies. Octavia tells Ilian she isn’t the girl he wants her to be and she promises that when she sees him again she will kill him.
Nonetheless, Ilian surreptitiously follows Octavia through the streets of Polis. When Octavia is cornered by three champions, Ilian ambushes them to save her. The five warriors fight with each other in a violent and vicious melee battle. Eventually, when the Boudalan champion hurls his pike weapon at Ilian, the latter ducks under the blow and the weapon kills the Delphi champion when it strikes her in the chest. Ilian is then able to kill the Boudalan champion with a blow to the head and Octavia dispatches the third enemy champion (this one from the Broadleaf clan) by cutting off his hand and ramming her sword through his face. Octavia is angry at Ilian for not staying away from her points out that at least one of them will have to die. “I didn’t follow you”, states Ilian, “Trishanakru needed me”. Suddenly, Ilian is struck in the neck by an arrow, and Octavia hurriedly drags him to cover. It is immediately obvious however that the wound is severe, as the arrow has crippled Ilian and he gasps to Octavia that he can’t feel his legs. Ilian pleas for Octavia to kill him, just as she said she was going to; “that’s not what I meant”, grieves Octavia. “You promised”, Ilian replies. Reluctantly, Octavia draws her knife and stabs Ilian through the heart.
Initially, Ilian was angry at the death of his family and was determined to avenge them. As a result of his enslavement by A.L.I.E., he also despised technology and was obsessed with destroying anything to do with it. However, after he burned Alpha Station, formed a bond with Octavia, and learned of the approaching Praimfaya, he attempted to return to a more peaceful life on his family's farm. Ilian was very loyal to his clan Trishanakru and his heritage.
Ilian was strong, well built, and had brown, shoulder length hair. He also had eight black dots in the middle of his forehead.