CW's: The 100

Portrayed by Bob Morley, Bellamy Blake is Octavia's brother.^[5] He professes a strong determination to protect his sister, spanning from her birth. He often says 'my sister, my responsibility'. He was the leader of the 100, although often loses focus and control over the group, and uses militaristic approaches. He develops from an antagonistic character to an antihero, realizing the 100 matter to him and showing compassion towards enemies and fallen comrades.
He initially clashes with Clarke over their opposing approaches to their respective responsibilities over their people, but ultimately both he and Clarke develop a mutual respect and learn to compromise for each other's methods. He still feels guilty for getting Octavia caught, which led to her lockup and his mother's death.
In the third season, he aligns himself with the new Chancellor after a grounder clan bombed Mount Weather, killing 49 people, including his girlfriend. In the process he betrays Marcus Kane and put the whole of The Ark at risk of death. The bombing was made possible because Bellamy trusted Echo, the grounder who saved his life in the previous season, and listened to the false information she delivered. He helps to put in prison his sister's boyfriend Lincoln, which leads to Lincoln's execution. After Pike's election, Bellamy is one of the nine guards (along with Pike himself) that carry out the chancellor's orders to kill the 299 grounder warriors sent by Lexa.

Portrayed by Christopher Larkin, Monty Green^[5] is a smart and tech-savvy teenager who is a valuable asset to the teenagers on Earth due to his pharmaceutical and engineering knowledge. He and Jasper were arrested for making illegal substances. He is best friends with Jasper and is among the 48 held in Mount Weather, eventually escapes and reunites with his mother in season three. He tries to help Jasper recover from the traumatic events in Mt. Weather, although he blames Monty for the death of Maya, his love interest. He eventually becomes part of Chancellor Pike's cause after his friend Monroe is killed by the grounders. In the process he gets Marcus Kane put in prison and Lincoln killed. He eventually betrays his mother and Pike in "Stealing Fire" by helping Kane, Octavia, Harper, Miller and Sinclair escape by feeding members of the Ark Guard faulty intel and distracting them. In "Nevermore", Monty is forced to kill his mother—who had taken A.L.I.E.'s key—after she nearly kills Octavia. In "Red Sky At Morning", Monty has sex with Harper in Arkadia, and is forced to delete and essentially kill his mother for a second time by wiping her memory from the city of light, In season 4 he comes up with the idea of protecting his people by shielding Arkadia with a hydrogen generator and recruits Bellamy, Harper & Miller to gather it when they do they blow it up to rescue the slaves taken by the ice nation, there he learns that the Chief killed his father and instead of killing him himself he allowed the slaves vengeance by freeing them, After realizing Harper chose to stay behind in Arkadia he decides to stay with her until she changes her mind, she is eventually convinced and they search for more people to recruit.

Portrayed by Devon Bostick, Jasper Jordan is a goofy and geeky chemist. He is Monty's best friend. After his capture and subsequent rescue from grounders, he becomes traumatized by his near-death experience which he struggles to overcome. Early in the series, he has a crush on Octavia, even saving her life during an animal attack, but she offers her friendship in return instead. He was one of the delinquents' camp's gunners and is among the 48 held in Mount Weather, and becomes an acting leader of his surviving people in Clarke's and Bellamy's absences. Jasper later becomes romantically involved with a Mount Weather resident, Maya who was later killed. In grief, Jasper becomes an alcoholic and he is disgusted that his own people would steal from Mt. Weather after the war with its inhabitants as well as hating Clarke. Monty and Octavia struggle to help Jasper to cope with his loss, but although Jasper was briefly tempted by the city of light tablets, when he realised that they erased all good memories relating to painful topics, he refused to take one, even breaking Raven out of Camp Jaha and taking her to Clarke and other escapees for medical treatment to remove the chip. It is revealed that he has been chipped while on Luna's oil rig and turns on the 100 under ALIE's command. He is freed from her control once she's defeated. In Season 4, he attempts suicide only for Raven to tell him they only have six months to live. He eventually dies from an overdose.

Portrayed by Isaiah Washington, Thelonious Jaha^[5] is Wells' father and the former Chancellor of the Ark. Thelonious, along with Marcus, were best friends with Jake Griffin and his family. However, his and Marcus' friendship with the Griffins deteriorates after Jake's death and Clarke's subsequent arrest but he manages to maintain Abby's. He loses his power while on Earth as he clashes with Abby and Marcus over their views on the grounders in addition to the unconfirmed destination, the "City of Light". Along with Murphy, he leads a small group of his followers from Camp Jaha to find the city. Having discovered ALIE, the A.I. that controls the city of light, Jaha has become essentially the leader of ALIE's cult, manipulating others into joining the city of light to escape the pain of daily life, apparently unconcerned about the side-effects even when presented with clear evidence that the city of light erases even good memories to spare the users from psychological pain, such as Jaha having lost all memory of his son, he is soon freed from ALIE's control after her defeat, he becomes guilt ridden after he sees all the casualties in Polis due to him feeding everyone a chip, in season 4 he assists Clarke in being a leader for her people such as suggesting they find shelter in a lost bunker (only to discover it couldn't hold out radiation.) and telling everyone that if they want to survive the second nuclear explosion they must earn a lottery pick to ensure they will be on that list., he eventually comes to the realization the bunker was a decoy and the real one is in Azgeda so he decides to recruit Gaia on what she knows about the symbol on the token and eventually learns it's a key to open the bunker, he eventually finds it and successfully opens it.

Portrayed by Henry Ian Cusick, Marcus Kane^[5] is one of the Councillors on the Ark. When Thelonious Jaha was Chancellor, he was second-in-command. He, along with Thelonious Jaha, were friends with Jake Griffin and his family, but his friendship with them did not last after Jake's execution and Clarke's subsequent arrest. Though he initially supports population culls to extend life on the Ark, when Earth is shown to be survivable, he is guilt-stricken and works for everyone to survive in hopes of making amends of his past misdeeds. This, in addition to his mother's influence and death, affect his later actions of seeking peaceful and compromising solutions when governing his people after arriving on Earth; in the process he gains allies who respect his new approaches, rebuilds his friendship with Jake's wife Abby Griffin, and earns the grounders commander Lexa's trust. He initially sides with Thelonious Jaha, but with the former Chancellor now appearing delusional, ruthless and possibly insane, Kane aligns himself with Abby, who becomes Jaha's successor.

Portrayed by Lindsey Morgan, Raven Reyes (Recurring|Recurring, season 1; regular, season 2–) is an ambitious zero-gravity mechanic when on board the Ark who isn't afraid of anyone or anything. She later collaborates with Abby Griffin in her escape from the Ark and launches herself in a pod to Earth, and occasionally advises Abby in the fields in electronics and mechanical engineering after she becomes chancellor on Earth. Brave and intelligent, Raven leads the camp in setting up communications and making bombs. She was childhood friends with Finn and was in a relationship with him until he fell in love with Clarke. It is revealed in season two, that Finn took the blame for Raven's crime because she was already over 18 and would be floated. She was the first zero G mech student under the age of 18 in 52 years. In season 3, with Abby's help, Raven begins recovering from the injuries she sustained from last season. She joins Jaha's cause after reluctantly taking a tablet given to her by him, she does begin to fight the side effects after Jasper reminds her about Finn. She is soon saved by Clarke and freed of ALIE's control, In Season 4 she bonds with Luna for her loss and convinces her to help save everyone on earth, she also forgives Murphy for shooting her in the spine, later on it is revealed while taking the chip she is able to use 90% of her brain but caught a tumor that will leave to her having a stroke that might lead to death, she brushes it off and continues working, she later hallucinates Becca who tempts her with the chance to spacewalk leaving her to stay behind, A Sinclair hallucination appears to tell her to continue living which gives her the motavition to fight off Becca by restarting her heart, afterwards Clarke rescues her and request she fly them to The Ark in which she agrees to do.

Portrayed by Ricky Whittle, Lincoln (recurring, season 1; regular, season 2–3) is a grounder who rescues Octavia. The pair develop romantic feelings, and Lincoln helps the 100 multiple times, causing him to be viewed as a traitor to his people. He later is drugged to become a reaper, but with Clarke's and Abby's assistance, withdraws from the drug. Having been viewed as a traitor by some of his people, Lincoln resides in Camp Jaha with Octavia. He is put in prison by Pike with the help of Bellamy and shot by Pike after surrendering to save his fellow grounders from execution.

Portrayed by Richard Harmon, John Murphy (Recurring|Recurring, season 1–2; regular, season 3) starts out as one of Bellamy's men and is generally disliked by the group due to his reputation of being a troublemaker and career criminal, making him one of the few members to actually have committed felonies and not petty misdemeanors. After being wrongfully accused by Clarke and nearly lynched, he tries to kill Charlotte. As a result of her death, he is banished from the camp. He later returns, surviving being tortured by the grounders. He seems to have forgiven the 100, but he kills two and attempts to hang Bellamy and successfully shoots Raven in the spine. In season two, he helps the 100 as they search for their lost members, even saving Bellamy's life when he could have let him drop. As he is still disliked in Camp Jaha, he accompanies Thelonious to find the city of light. He eventually finds a lighthouse where he is trapped by Jaha and ALIE after watching something that horrifies him. He later leaves the Island after not wanting to be a part of Jaha's insane missions, and gets a boat ride from Emori. After Emori transports him and Jaha across the sea, he refuses to take the key and flees with Emori. They start robbing people in the Commander's Forrest and he is eventually captured by grounder warriors and brought to Polis after one of the captors discovers a chip in his pocket which has the "Sacred Symbol of the Commander" which is an infinity symbol. He is tortured for information by Titus and eventually tells him what he knows. Later on Titus tries to murder him and frame Clarke but accidentally shoots and kills Lexa. After she dies he witnesses Titus remove the chip. After Titus gives Clarke the chip and commits suicide, Ontari makes him the new "Flamekeeper" since he is the only other person to have witnessed it being removed from another person. Ontari takes a liking to him and wants him to sleep with her; if he refuses, she will kill him. He later reunites with Emori who is under ALIE's control, and ALIE implies to her that Ontari's had sex with him. After the City of Light is destroyed and ALIE's control over everyone dissolves, Murphy stays behind with Emori. When he finds out there's a nuclear disaster coming which will wipe out everyone on earth, he and Emori decide to side with Clarke, who has a plan that might save a 100 people. Murphy ends up helping Raven with another plan, and he is confronted with what he's put her through after he shot her. When Raven opts to stay behind, he has a rare emotional moment and shares a tearful goodbye with her.

Portrayed by Zach McGowan, King Roan (Recurring|Recurring season 3; regular season 4): An ice nation fugitive who is tempted by Lexa to kidnap Clarke. He is the son of Queen Nia, he later becomes King of the ice nation after Lexa kills Nia for attempting to overtake her. He supports Ontari as the new Commander and attempts to track down Clarke who has escaped with the Flame. Roan and Clake instead form an alliance to give Ontari the Flame to help shut down ALIE but the plan fails and Roan is shot by Kane, he is rescued when Clarke & Abby take the bullet out of his chest, Echo tries to tempt him to kill Clarke for her crimes as well as secure his position as ruler of the 13 clans, Clarke however gives him ALIE 2 in hopes that he will let her & her people live to save the planet from the nuclear explosion in 6 months which he accepts, later on he learns that Skaikru seems to be protecting themselves and thus ending the alliance, Clarke does convince Roan to share Arkadia until it explodes, He is drowned to death by Luna.