Clarke and Niylah is the relationship between Clarke Griffin and Niylah. They seemed to have met off-screen and Clarke has been trading with Niylah after she left her people back at Arkadia. During the course of Season 3 and 4, the pair sleep together twice. In Season 5, after not seeing each other for six years, they have both moved on but still care for each other. In Season 6, Niylah and Clarke are still friends. In Season 7 Niylah goes with Clarke and her team to find Bellamy, Octavia and Echo.
Clarke meets Niylah in the three months between seasons 2 and 3. Clarke is living alone and frequently trades at Niylah's shop because of its isolation. In "Wanheda (Part 1)", Niylah flirts with Clarke who accepts her advances and they sleep together, however Clarke leaves during the night. After "Wanheda (Part 2)", Niylah is not mentioned until "Nevermore" when Clarke needs a place to hide from A.L.I.E.
In season 4, Clarke and Niylah have regular contact. Niylah assisted the Sky People in preserving meat. In "The Tinder Box", Clarke convinces Niylah to stay in Arkadia. After Clarke leaves for Becca's Island, the pair do not see each other again until inside the Second Dawn Bunker. The guilt and stress of being a leader weighs heavily on Clarke and Niylah attempts to help her with emotional support. Clarke leaves the bunker shortly and they do not see each other for six years.
In Season 5, they reunite in "Exit Wounds". While Clarke had been avoiding her, the two remain friendly and show they care for the other. Both women have moved on and both have new families. Their loyalties have changed and Niylah believes in Wonkru and Octavia. Niylah figures out that Madi is a born Nightblood and intends to tell Octavia but gives Clarke one day to do it herself.
In Season 6, after the Battle against the Primes, "The Blood of Sanctum", Niylah is happy to see again Clarke alive.
In Season 7, Niylah goes with Clarke and her team to find Bellamy and Octavia.
In Wanheda (Part 1), Niylah helps run a trading post with her father. Clarke waits for her father to leave before she arrives with a black panther she has recently killed in the woods to trade for supplies. Clarke and Niylah chat in Trigedasleng and Niylah offers her a drink. Clarke notices Niylah is wearing one of the Delinquents' wristbands. Clarke asks Niylah about how she got the wristband, but they are interrupted by Roan and another warrior looking for Clarke. Roan notices Clarke before asking if Niylah has seen the woman in a picture he is carrying around. Niylah tells Roan that Clarke was there two days ago and that is how she got the wristband but Clarke left to travel north, following "Eden's Path" into the Ice Nation. Roan and the other warrior leave to find Clarke. Clarke asks Niylah when did she figure out who she was and Niylah tells her since the beginning. Niylah switches to English and offers her a drink again while they wait for Roan and his companion to leave. Clarke asks why Niylah is helping her. Niylah reveals that her mother was taken by the Mountain Men and Clarke stopped the Reaping.
Niylah later helps Clarke clean the wounds she sustained while killing the panther. Niylah asks about the Mountain and Clarke says she did what she had to do. Niylah tells her she wiped out their greatest enemy by herself. Clarke kisses Niylah and they have sex.
In Wanheda (Part 2), Niylah is seen being beaten and thrown around inside her trading post by Roan's partner. The Grounder wants to know where Wanheda, Clarke, is. However, Niylah refuses to give him any information. The Grounder pulls out a knife and says he will only ask once more, and then threatens to cut off her hand if she doesn't tell. Before she can answer, Bellamy, Kane, Monty, Hannah, Indra, and Pike enter the room. Bellamy shoots and kills the Grounder. Indra realizes that the Grounder was a bounty hunter. Indra then reassures Niylah that they are there to help and tells her that they are looking for Clarke, but she points out that he was, too, gesturing to the deceased bounty hunter. Niylah recognizes them as Skaikru, as Bellamy begs her to help them. Niylah ends up telling them that Clarke had been there last night, but that she was gone when she woke up. Kane asks Niylah if Clarke gave her any indication of where she was headed, and Niylah says she didn't but the bounty hunter did. Niylah then explains that the bounty hunter claimed that his partner from Ice Nation came back for her. She wishes them the best of luck before they leave.
In Nevermore, Clarke and the group need a wristband to fry A.L.I.E. from Raven's mind. So they go to Niylah and when she refuses to help them, Bellamy aims at her and violently tells her to let them in. Later, when possessed Raven reveals that Bellamy was the one who slaughtered her father, Niylah runs in and slaps Bellamy exposing their location to A.L.I.E.
After Raven is freed from A.L.I.E and the group is leaving, Clarke tells Niylah to stay safe from the AI and Octavia trades a lantern for a new outfit and Niylah nods.
Clarke and Niylah started off as friends and sexual partners, but did not pursue a romantic relationship beyond that. Events (primarily the plot) broke them apart. In the next season Clarke is seen to first be excited to reunite with Niylah but with the Second Nuclear Apocalypse looming, they again are torn apart. After six years, they meet essentially as strangers again and have little interest in getting into a sexual relationship again. Niylah even becomes an "antagonist" in Clarke's plotline in Season Five.