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Death to Primes.
— His last words. [src]

Cillian was a minor character in the sixth season. He was portrayed by Carlo Marks and debuted in "The Children of Gabriel".

Cillian was a doctor in Sanctum, but he was secretly a spy of the Children of Gabriel.

Early Life

Over 200 years after Mission Team Alpha founded a settlement, he was born as a red-blooded carrier of the black blood gene, and during his adult life he became a doctor.

Throughout the Series

In The Children of Gabriel, Russell Lightbourne tells him that the seaweed got to Murphy during the red sun. Cillian takes out a Kepa-She (Snake) and lets it bite Murphy. The snake's venom degrades the seaweed, reviving John Murphy.

Later, in the greenhouse he examines Clarke's arm. He is told by Russell to find the Children of Gabriel.

In The Face Behind the Glass, he is first seen coming to Blythe Ann's bar to examine Delilah and Clarke Griffin after their incident with the Children of Gabriel. He questions Delilah on what she remembers and she says everything. Then he tells her she's good to go and it will be like it out it never happened. He then looks at Clarke's hand wound and tells her to keep it hidden or people will worship her. He flirts with Clarke as he leaves. Madi tells Clarke that Cillian is cute. Clarke just brushes her off.

Later that night at the Naming Day party Clarke is dancing when Cillian approaches and asks her to dance, as Bellamy and Echo are watch from a distance. He dances with Clarke, then asks her to go back to his home with him. She does and they have sex. She fell asleep and wakes up to see Cillian looking out a window. They converse about the ceremonies taking place. He quotes a line from and tells Clarke that "The Crucible" was Gabriel Santiago's favorite play. She asks him what it means and he says it means there's two sides to every story. She asks what's the other side and he tells her that he going to take her to the Children of Gabriel to save her from Russell Lightbourne and the Primes. She tries to escape and knocks a glass out of the window and it lands on the ground alerting a guard. He then shoots Clarke with a parylitic dart and carries her to the bed. He tells her he's trying to save her and rubs some sort of cream on his arms, face and legs and says hopefully it'll keep him alive long enough to get Clarke through the radiation shield to the Children of Gabriel. Just then two guards barge in his home and ask him if he's going somewhere. Cillian protests that he will do anything to stop the Primes, even if he has to kill himself to do so and he slits his own throat.


He has a nice, quiet and calm demeanor and is willing to help others. He doesn't appear to be afraid of the Kepa-She snakes and he knows how to handle them. However, his behavior was meant to mask his true beliefs as an agent for the Children of Gabriel.

Physical Appearance

He has dark brown hair which is combed back, a short, scruffy, beard and brown eyes. He has a muscular but slender build and pale skin.


Russell Lightbourne

At first, he appeared to be very loyal to his leader, Russell.  They were usually seen together and seemed to share a mutual respect and trust with one another. However, later on, Cillian reveals that he resents Russell and all of the other Primes, and admits he stands by the motto "Death to Primes". 

Clarke Griffin

Cillian took an immediate liking to Clarke. He successfully courted her during the Naming Day ceremony and slept with her that night. However, he revealed that his primary goal was to take her to safety to the Children of Gabriel

Clarke and Cillian go to make out while everyone else is at Delilah's ceremony. Cillian mentions how the devil was kicked out of heaven and tries to compare the devil to Gabriel. He starts talking about the Children of Gabriel's cause. He says that not everyone within Sanctum believes in the divinity of the Primes. When Cillian gets up, Clarke notices his drawing book. There's a drawing with every member of Clarke's group. Clarke's image is circled while some like Bellamy and Murphy have an X. Clarke easily figures out that Cillian is keeping track of those with Nightblood. Based on the drawing, Cillian hasn't figured out that Madi is a nightblood yet. Cillian returns and notices Clarke with the drawing. He admits that he's identifying those with Royal Blood. As things get tense, Cillian shoots Clarke with a paralytic dart. The guards outside hear the commotion and come to check in. When they try to arrest him, Cillian commits suicide by slitting his throat. Before dying, Cillian begs Clarke to not give the Primes another host.


Season Six
Episode Appearance Status
Red Sun RisingAbsent
The Children of GabrielAppears
The Face Behind the GlassAppears
The Gospel of JosephineMentioned
Memento MoriAbsent
The Old Man and the AnomalyAbsent
What You Take With YouAbsent
Ashes to AshesAbsent
Adjustment ProtocolAbsent
The Blood of SanctumAbsent


Cillian: "Trust me, I know, but the venom degrades too quickly to deliver it in any other form."
-- The Children of Gabriel.
Cillian: "Death to Primes."
-- The Face Behind the Glass.

Killed Victims

  • Himself (suicide, slit throat)

Notes and Trivia

  • He knew how to use the Kepa-She, a type of snake.
  • He had red blood, but as a black blood gene carrier, he got a job as a doctor.
  • He is the first person to pretend to be a citizen on Sanctum while being a loyal member to the Children of Gabriel.


See Also

The 100 Characters
Main Characters
Abigail GriffinBellamy BlakeCallie CartwigClarke GriffinEchoFinn CollinsGabriel SantiagoHope DiyozaJasper JordanJohn MurphyJordan GreenLincolnMarcus KaneMonty GreenOctavia BlakeRaven ReyesRoanSheidhedaThelonious JahaWells Jaha
Recurring Characters
AdenA.L.I.E.AndersAnyaBecca FrankoBill CadoganBlythe Ann WorkmanBreeBrellBryanByrneCage WallaceCarl EmersonCassiusCharles PikeCharmaine DiyozaCillianCostaDante WallaceDavid MillerDiana SydneyDoucetteEmoriEric JacksonEthan HardyFoxGeoff HardyHannah GreenHarper McIntyreHayesIlian‎IndraJacapo SinclairJadeJae WorkmanJames CrockettJosephine LightbourneJake GriffinJeremiahJohn MbegeJonesKara CooperKaylee LeeKyle WickLeeLevittLexaLorelei TsingLucaLunaMadi GriffinMaya VieMichael VinsonMiles ShawMiranda MasonNathan MillerNelsonNiaNiylahNykoOntariPaxton McCrearyPriya DesaiRileyRoseRussell LightbourneRyker DesaiSeikuShawn GillmerShumwaySierraSimone LightbourneSterlingTitusTreyTristanVera KaneVincent VieZoe Monroe
Minor Characters
AdriaAnkaraArtigasAtomAurora BlakeAtohlCarisCaspianCharlotteChaseChrisCillianCole McAdamsConnorCostiaCraigCuyler RidleyDaniel LeeDaxDelanoDelilah WorkmanDerekDerrickDiggsDrewFioGideonGina MartinGlen DicksonGuaraGustusJuelKeenan MykulakLaylaLeeLieutenant GracoMacallanMark and Peter ColtonMelMiss LucyMylesNygelOsiasOtanPascalPennPeri GordonQuintRedReese LemkinRichardsRivoRoma BraggRyderScottSemetSgt. LovejoyShaySiennaStevensTor LemkinToshTrinaTrisTybeWhitmanWillaZoran