In Inclement Weather, Nyko helps save Octavia Blake from the poison in her system by giving her the antidote. He reveals that he only did it because he was friends with Lincoln. When Nyko refuses to help Octavia save Lincoln, she knocks him unconscious and holds him captive. Octavia barters with Indra Nyko's life for Lincoln's. When Indra does not appear with Lincoln at the meeting place on time, Nyko comments that Octavia will have to kill him now. Indra and Lincoln then show up and the two prisoners are exchanged with Octavia apologizing to Nyko. When the Reapers appear, both Nyko and Lincoln are taken away.
In Reapercussions, Nyko is saved along with a few others from the Reapers by Octavia, Indra, Artigas, and some other Grounders. Nyko tries to comfort Octavia after she finds out that Lincoln didn't make it to safety. He tells her that Lincoln was a good man. Nyko also reassures Octavia that she has proved herself and won't be killed.
In Human Trials, Nyko is woken from his sleep after a fire occurs in his village. The fire was made by Finn for a distraction. Finn and Murphy hold a Grounder at gunpoint and demand to speak to the leader of his Clan. Nyko steps forward and tells them that their leader isn't there right now but they can deal with him. Finn and Murphy end up taking all the Grounders hostage, including Nyko and begin to search the village for their friends. Nyko tries to explain that the Delinquents aren't there but Finn finds some of their belongings. Nyko tries his best to keep everyone calm. It works at first until one of the grounders tries to run away and Finn murders him. Soon, everyone starts panicking and trying to flee. Finn guns down many of the Grounders as they try to escape or attack, however, Nyko continues trying to protect his people. Once Finn stops shooting, he rushes to Artigas, cradling his lifeless body as Octavia approaches.
In Long Into an Abyss, like Lincoln used to do in the past, Nyko leaves a white flower outside the camp for Octavia to see. He warns Octavia their scouts have already arrived and the Commander will kill them if they do not leave. He asks her to let him save her life as she had saved his and it is something that Lincoln would have wanted. They are interrupted by sounds coming from the drop ship and Nyko realizes his friend had become a Reaper. He enters the drop ship with Octavia and sees Lincoln seizing. He pulls out a vial and begins to give a drop of the liquid to Lincoln while saying, Yu gonplei ste odon ("Your fight is over"). Clarke immediately realizes that Nyko is trying to mercy-kill Lincoln and stops him. Nyko tells them that death is the only way to stop his friend's suffering because he's never seen one come back from being a Reaper. Finn arrives, the man who had massacred Nyko's village. He attacks Finn, stating, "Blood must have blood!" He is temporarily knocked out by Clarke hitting him with an Ark Guard stun stick. After they restrain him, Nyko watches in amazement as Clarke resuscitates Lincoln, seemingly back from the dead. This gives Clarke the idea to discuss an alliance with the Commander in exchange for saving the Reapers. After Lincoln appears to die again, Nyko witnesses Abigail Griffin electrocute Lincoln with the shock baton back to life a second time.
In Remember Me, Nyko is present at the Grounder and Sky People alliance feast and tries to help Gustus when he is poisoned. He later returns with Indra tells the others that Gustus will be fine. After Raven is being punished as the one who tried to poison Lexa, he tells Lincoln they need to run now and he will try to protect him. When Clarke asks for the bottle suspected of poisoning Gustus, Nyko fetches it for her.
In Resurrection, Nyko aids the wounded at Tondc with Abigail Griffin. Nyko struggles with helping one of his fellow Grounders and he has to leave one of them to die. When Indra is shot, Nyko helps her while Lincoln distracts the sniper shooting at the Grounders. Later, he advises Indra that she's not yet ready to march on Mount Weather but she tells him she won't miss the fight.
In Wanheda (Part 2), Nyko rides up to Arkadia on a horse, dying. Lincoln and Octavia rush to him and notice a severe and deep gash on his side. Lincoln demands to know who did it, and Nyko informs them that it was Azgeda. Lincoln and Octavia help him off of his horse and bring him to Abby. Abby realizes that Nyko will need a blood transfusion, so Jackson takes some of his blood to see what blood type he is. Jackson states that Nyko is Rh null. Octavia offers her blood for Nyko but Abby says Rh null can only take Rh null. Lincoln allows Jackson to check his blood type but he doesn't have Rh null either. Jackson says that Mount Weather will have the blood they are looking for, and after a short debate, the gang decides to take Nyko there. Later on, Abby manages to save Nyko's life and he wakes up, thanking her for saving him. Lincoln tells Nyko "Welcome back, Brother" in Trigedasleng and takes Nyko's hand. Lincoln mentions that the only way to save him was to bring him to the Mountain, and tells Jackson and Abby that his people will only see death there. Nyko argues that they can convince their people to change their minds, and reminds Lincoln that places aren't evil; people are.
In Watch the Thrones, he leads the sick grounders who Abby had agreed to help into Arkadia.
In The Four Horsemen, Nyko approaches the gates of Arkadia with a group of sick grounders and pleads with the guards to give them entry so they can be treated by Skaikru medicine (as the illness is beyond Nyko’s skills to treat). Clarke approaches the group and asks Nyko what has happened, Nyko, who is not sick himself, recounts that they lost more than 40 people to the sickness before reaching Arkadia. Bellamy comes forward and recognises one of the sick grounders as Luna, the leader of Floukru and Luna begs the Arkers not to turn away her and her people in spite of the reason that she didn’t aid them in the A.L.I.E. conflict. Abby, the Sky People’s head doctor arrives and recognises the symptoms of the grounder’s illness as ARS (acute radiation sickness). When Abby asks Luna when the symptoms started, Luna replies that it was right before the fish started dying, Nyko elaborates by saying that dead fish are floating on the surface of the ocean all the way to the horizon and in every direction. Abby declares that the sickness isn’t contagious and orders the grounders be taken to med bay; Nyko helps carry one of the sick grounder children, Adria, there.
Nyko comforts Luna and Adria as they lie in their sickbeds. When Jackson and Abby come over with medicine, Nyko helps Adria sit up so she can swallow a pill. Nyko asks the doctors about the other sick people and is told by Jackson that Adria will be monitored closely and if her symptoms improve then they will threat the other patients the same way.
One by one Luna’s people succumb to the radiation sickness and despite receiving the Skaikru drugs, Adria’s condition worsens and she too eventually dies in Luna’s arms. “Yu gonplei ste odon”, Nyko says the grounder words that accompany death and then consoles a devastated Luna.
Emotionally exhausted, Nyko slumbers in a chair, but when he awakens he finds that astonishingly, Luna is still alive and appears to be cured from her sickness. Nyko asks Abby how it is possible for Luna to be healed; Abby deduces that it must be because Luna is a Nightblood.
In A Lie Guarded, Nyko accompanies Luna, Abby, Jackson, Raven, Murphy, Emori and three Ark guards under the command of Nathan Miller to A.L.I.E.’s island to locate Becca’s research lab in the hope that they should be able to use it to manufacture Nightblood as a defence against the forthcoming nuclear apocalypse. When Nyko disembarks from Emori’s boat he praises Luna for doing the right thing in helping Skaikru and reassures her that they are good people and can be trusted. Nevertheless, Luna is suspicious of the Sky People’s intentions and only came because she didn’t think that they would give her a choice in the matter. Miller hurries the group along and as they walk across the shore they come to a line of obelisks which Emori tells them is a boundary set by A.L.I.E. upon which no mutants were allowed to cross. Having to cross the boundary to get to the lab, the group head inland but almost immediately hear a buzzing sound which is revealed to be one of A.L.I.E.’s drones, still active despite A.L.I.E.’s termination. The drone hovers over the group for a moment and then suddenly opens fire – killing one of the Ark guards with a shot to the head. Straightaway, Nyko and everyone else run to seek shelter, but both he and Luna are separated from the others and find themselves exposed in the open, with one of the drones targeting them and not enough time to flee to shelter. In a courageous act of selflessness, Nyko shields Luna from the drone with his own body and is shot multiple times in the back before Miller is able to shoot down the drone.
Nyko is friends with Lincoln and considers him a brother. Nyko was willing to help save Octavia and go against his own people even though he could be punished for it in order to help Lincoln. He was willing to mercy-kill Lincoln when he thought Lincoln had irrevocably turned into a Reaper. After Gustus is poisoned and the Sky People are blamed, Nyko tells Lincoln it is no longer safe for them in Tondc and they say their goodbyes before Clarke discovers Gustus actually poisoned himself.
Nyko provides Octavia with the antidote for the poison in her arrow wound after Lincoln gets captured by their people for being a traitor. When Octavia learns that Nyko will not help save Lincoln, she takes him hostage and barters his life for Lincoln's. Nyko doesn't seem angry with her for taking him hostage and she apologizes for it later on. Nyko again tries to save her by warning her to leave the area before Lexa arrives to start her war against the Sky People.
Indra is Nyko's Chief and Nyko is a Healer for Indra's clan. Indra was willing to exchange Lincoln for Nyko when Octavia held him captive. She later leads a rescue mission to find him after the Reapers take him at the end of Inclement Weather. She's relieved to have found him and helps him to his feet in Reapercussions. Nyko helps save her life in Resurrection after she is shot by a sniper.
Artigas goes along with Indra on the mission to rescue their captured warriors from the Reapers because his dad was one of the Grounders taken, along with Nyko. In Human Trials, Nyko tries to calm Artigas when Finn Collins and John Murphy entered their village with guns. When Artigas tries to escape and gets shot, Nyko rushes to his side and cradles his lifeless body as he glares at Finn with anger.
Nyko: "Our scouts have already arrived. The commander is true to her word. If you do not leave, you will die. Octavia, you saved my life from the Reapers. Now let me save yours. It's what Lincoln would have wanted."