History Series / The100

** It gets to the point in Season 5 that most of the characters can't tell where they fall anymore, and Bellamy of all people has become TheHero.

** Season 6: [[spoiler:Shaw, Kane and Abby.]]
** Season 7: [[spoiler:Bellamy, Gabriel, Diyoza, Sheidheda, Cadogan, Russell and Nelson.]]

* BackForTheFinale: The "judge" appearing as Lexa (for Clarke) and Abby (for Raven) in the [[GrandFinale series finale]].

* DreamingOfThingsToCome: "Bitter Harvest" opens with Lexa being woken from her sleep by a nightmare of the deaths of the previous Commanders. Clarke assures that it was just BadDreams, but Lexa believes that [[TalkingInYourDreams it is a warning from the Commanders]]: They believe she is betraying their legacy.

** It becomes somewhat relevant again in Season 4, with [[spoiler:Arkadia only having enough space for 100 survivors. However, it becomes a moot point when Arkadia is blown up.]] Several episodes later, [[spoiler:Octavia declares that each clan will get 100 spots in the bunker.]]
* ArtificialIntelligence: It's eventually revealed that the nuclear apocalypse was caused, not by nations going to war, but by a [[AIIsACrapshoot rogue A.I.]] called Alie hacking the world's nuclear weapons systems, in an effort to curb overpopulation. She becomes the BigBad of Season 3, where she continues her misguided efforts to help humanity by turning all surviving humans [[AssimilationPlot into computer based consciousnesses as well]], whose [[LaserGuidedAmnesia memories]] and [[EmotionControl emotions]] can be edited to [[GettingSmiliesPaintedOnYourSoul create perfect happiness]], [[TheEvilsOfFreeWill free will be damned]].
** The Commanders of the Grounders and the Primes of Sanctum are also revealed to be artificial intelligences, albeit created by BrainUploading human minds onto computer drives.

* AssimilationPlot: Alie, an ArtificialIntelligence, attempts to force all human beings to ingest a computer chip that will connect them to the City of Light: a {{Cyberspace}} reality where they will [[BrainUploading continue to exist as computer programs even after their physical bodies are killed]], and where Alie can use EmotionControl and LaserGuidedAmnesia to make them [[GettingSmiliesPaintedOnYourSoul perfectly happy, whether they want to be or not.]]

** Season 7 [[spoiler: and the series ends with Sheidheda and Cadogan dead, and the Judge ascending humanity after Indra and Octavia convince both sides to stop fighting. However, Clark is barred from ascending as she killed Cadogan during the test, leaving her the last human left in existence... or so it seems. In an interesting turnaround, however, Clarke's friends (Raven, Octavia, Gaia, Indra, Jordan, Echo, Hope, Murphy, Emori, Jackson, Nathan, Niylah, and even Levitt) all rejected transcendence in order to be with her again despite knowing that they won't be allowed to create children to continue the species and they won't be able to transcend with the rest of humanity after they die. With no one else to fight, their fight is finally over.]]

* {{Cliffhanger}}: After wrapping up the storyline main of each season, they love to leave a little cliffhanger to introduce the BigBad of the next season:

** Season 2ends with Jaha and Murphy having made their way to an oddly intact mansion on an island. Murphy sees a video telling how [[spoiler:an AI got nuclear launch codes nearly a century ago, while Jaha meets the AI itself.]]
** Season 3 has the revelation that ALIE was [[spoiler:uploading human minds to the City of Light in order to make sure they would survive Praimfaya, a wave of fire and radiation that would likely kill everyone within six months.]]

*** [[spoiler: Sheidheda has been removed from the flame, saving Madi, but escapes, presumably to take over the Eligius IV ship.]]

** Season 7 [[spoiler: and the series ends with Sheidheda and Cadogan dead, and the Judge ascending humanity after Indra and Octavia convince both sides to stop fighting. However, Clark is barred from ascending as she killed Cadogan during the test, leaving her the last human left in existence... or so it seems. In an interesting turnaround, however, Clarke's friends (Raven, Octavia, Gaia, Indra, Jordan, Echo, Hope, Murphy, Emori, Jackson, Nathan, Niylah, even Levitt, and especially Madi) all rejected transcendence in order to be with her again despite knowing that they won't be allowed to create children to continue the species and they won't be able to transcend with the rest of humanity after they die. With no one else to fight, their fight is finally over.]]

** Season 7 [[spoiler: and the series ends with Sheidheda and Cadogan dead, and the Judge ascending humanity after Indra and Octavia convince both sides to stop fighting. However, Clark is barred from ascending as she killed Cadogan during the test, leaving her the last human left in existence... or so it seems. In an interesting turnaround, however, Clarke's friends (Raven, Octavia, Gaia, Indra, Jordan, Echo, Hope, Murphy, Emori, Jackson, Nathan, even Levitt, and especially Madi) all rejected transcendence in order to be with her again despite knowing that they won't be allowed to create children to continue the species and they won't be able to transcend with the rest of humanity after they die. With no one else to fight, their fight is finally over.]]

* FamilyUnfriendlyAesop: In "Murphy's Law," it's flat-out stated by Clarke that sometimes you should lie to people because at times telling the truth might cause too much misery.

** Season 7: [[spoiler:Bellamy, Gabriel, Diyoza, Russell and Nelson.]]

** Clarke who had a major fight with Anya in season 2 and won. In season 3, she killed a panther with just a knife.

* AdvancingWallOfDoom: The main threat of season 4, [[spoiler:the Praimfaya wave. The nuclear reactors in Europe are finally breaking down, releasing huge amounts of radiation, which are estimated to reach the main setting in mere months. Everyone scrambles to find some way to survive it, as this is a force that simply cannot be beaten.]] The main solution turns out to be [[spoiler:avoiding it by going down to an underground bunker and wait for five years]], while another group, cut off from the others, manages to [[spoiler:go over it by heading up to the remains of the Ark.]]

* ArcNumber: [[TitleByNumber 100]]. It's the number of delinquents originally planned to be sent down to earth, the number of slots left [[spoiler:in Arkadia in season 4, and the number of representatives each clan gets to send to the bunker.]]

** It becomes somewhat relevant again in season 4, with [[spoiler:Arkadia only having enough space for 100 survivors. However, it becomes a moot point when Arkadia is blown up.]] Several episodes later, [[spoiler:Octavia declares that each clan will get 100 spots in the bunker.]]

* AssInAmbassador: In season three, the Ice Nation has become belligerent and intends to break the Grounder Coalition. Their ambassadors are condescending and hostile to the other Grounder tribes and the Sky People. One of them gets himself thrown off a balcony for his arrogance, but that has no tempering effect on the others.

** This becomes a major plot point at the end of season 4 [[spoiler:with regards about what to do with a bunker that can support 1200 people now that the approaching Praimfaya wave is unavoidable and it is the only hope for humanity's survival. In order to avoid a full-on war between every clan, Roan proposes that a Conclave should be held with a single Champion selected from each clan and that the winner will be allowed to utilize the bunker however they see fit. Octavia ends up winning the Conclave and, after declaring that all clans will be allowed to live in it together, is pronounced the leader of Wonkru.]]

* BeardOfSorrow: Jasper starts season 3 in a depressed funk with a goatee. This is in stark contrast with the preceding seasons, in which his clean-shaven face emphasized his innocence.

* BeneathNotice: At the start of season three, Clarke is hiding in the wilderness and avoiding both Arkadia and the Grounder Coalition. Since she is living as a normal Grounder, speaking Trigedasleng and hunting for her own food, occasionally exchanging animal meat and skin for goods at a trading post, nobody thinks that she might be the person everybody is looking for. [[spoiler:[[SubvertedTrope Roan sees through the disguise and captures her regardless.]]]]

** The season 2 finale is more a DownerEnding, see below. But it is also bittersweet since Clarke and Bellamy do accomplish the goal of saving their people from Mount Weather, and the prisoners get to reunite with their loved ones.
** The season 3 finale. [[spoiler: The City of Light is destroyed and people reunite with their loved ones, but Clarke has to finally say goodbye to Lexa, and A.L.I.E. reveals to her that radiation from nuclear plant meltdowns is going destroy the earth again in about six months.]]

** The Mountain Men engage in sadistic medical experiments upon the innocent and will not even discuss potential alternatives, not hesitating even when a peaceful solution is literally shouted into their faces. This also doubles as GrayAndGrayMorality because the atrocities are carried out because they are genuinely the only way for them to survive - the Mountain Men have no tolerance for the surface radiation on the earth, and the only treatment is derived from the blood of kidnapped grounders. Later, they find that the people of the Ark can potentially cure them completely, but only with their bone marrow - leading them to attempt to kill dozens of teenagers in an attempt to protect themselves from radiation.

* BlueAndOrangeMorality: In season 3, we are introduced to A.L.I.E., an [[ArtificialIntelligence artificial intelligence]] whom Jaha is helping to shepherd the citizens of Arkadia to the "City of Light," a rumored promised land. To enter, a person must swallow a device that hardwires the brain into feeling absolutely no pain, physical or otherwise, wiping entire sections of memory and essentially turning people into drones for her. As an artificial intelligence, she has no human emotions or human understanding of right and wrong and is just following her core command, which is to "make life better for humanity." She takes drastic measures to accomplish this, including wiping out most of mankind before the events of the series to prevent a potential overpopulation problem. It is later revealed that her purpose for the City of Light was to [[spoiler:"save humanity" from a coming nuclear deathwave that will irradiate the ground in six months' time. Taking away pain was an attempt to give people happy lives, and after the end came, their minds would have lived on in the city,]] but as a machine, she couldn't understand what exactly was wrong with the violent ways she went about getting people to enter.

** In season three the concept gets an explicit discussion between Clarke and Lexa when they both wonder if, someday, they might not be able to lead their own individual lives without needing to worry about the needs of their people as well.
* ChallengingTheChief: There is a [[PlayingWithATrope variation]] in season 3. Queen Nia of the Ice Nation challenges Lexa's position as the Grounder Commander and selects her son to fight Lexa in a TrialByCombat. However, neither Nia nor Roan can become the new Commander if Lexa is defeated: the title will instead descend onto one of the [[RoyalBlood Nightbloods]]. Nia hopes that Ontari, an Ice Nation Nightblood, will become the new Commander.

** Finn begins the series as a charming, devil-may-care rebel but becomes TheConscience of the group, before descending into obsession in season two.

** Jasper is awkward and dorky at the beginning, but is forced to grow up considerably in season two after becoming the ''de facto'' leader of the 47 survivors in the Mountain. The events of the second season finale were especially hard on him. The third and fourth seasons continue following his downward spiral due to the copious character deaths in the series.

** Murphy starts out as a sadistic bully, is banished for it, and returns from his exile as a violent sociopath. But throughout season two he learns to appreciate the help of others and skills he can offer them in turn, and by the events of the third and fourth seasons, he gradually becomes a [[HeelFaceTurn mostly trusted main character]] - albeit a somewhat amoral one.

** After the 100 are joined by other members from the Ark, they are absorbed back into the official political structure headed by the Chancellor. Clarke, however, retains a position of power due to her history and influence with the Grounders. It culminates in a standoff in season two, where she speaks the line "You might be the Chancellor, but I'm in charge". In season three, her reputation as Wanheda, "The Commander of Death", continues to give her elevated standing with the Grounders and the Ark.
** Season two introduces the the mysterious figure of "The Commander", who rules over all the Grounders. Though it is initially implied to be the older Gustus, it is actually Lexa, a young woman who has already been in command for years.
** By the end of season 4 Octavia ends up becoming the leader of [[spoiler:Wonkru, comprised of what is essentially the last remnants of humanity (as far as they know anyway).]]
** In season 5, [[spoiler:the Flame passes to Clarke's preteen adopted daughter Madi, the last known natural nightblood, and she leads Wonkru in the last episode.]]

** In season 5, the survivors in the bunker quickly realize that the hydroponic farms will not be able to feed everyone. A group tries to seize the floor with the farms and lock the others out and they are only stopped due to [[spoiler: Jahu's]] HeroicSacrifice. The population is then reduced by having criminals fight a DuelToTheDeath. When there is a bad harvest and the food situation turns critical, the leaders order [[spoiler: the cannibalization of the dead for food]].

** The conflict in season 5 is completely unnecessary as the valley could support both populations. However, Wonkru and the convicts do not trust each other and each fear that if they lay down their weapons, the other side will enslave them. Clarke, Bellamy and Kane try to find a peaceful solution but cannot convince the leaders of the two groups.

* DontMakeMeDestroyYou: Through the back half of season two, Clarke emphasizes to Lexa and the Grounders that their war with the Mountain is against its leaders and its policies: They will not slaughter its entire population. Once the engagement begins in earnest, she repeatedly asks their leaders to stand down or surrender instead of forcing her to kill them all. The Mountain refuses to negotiate, [[DownerEnding and she is forced to kill everybody]].

* DownerEnding: The two-part season 2 finale has Mount Weather releasing their Grounder prisoners as part of a deal with Lexa which results in her taking her army and going home, leaving Clarke and the others to fight Mount Weather alone with some of their people about to have their bone marrow extracted and killed in the process. This forces Clarke into an escalating duel of wills with Cage Wallace, which eventually leaves her with no choice but to flood the mountain with radiation and kill all within, including Maya and several other innocents and allies. The remaining Sky People finally return home but Clarke can't bring herself to join them. In the B-plot, Jaha discovers that the nuclear warhead from the missile he rode to the ground has fallen into the possession of the [[AIIsACrapshoot insane A.I.]] that started the nuclear war in the first place and she wants his help with a unknown goal that will effect everybody.

* DoubleStandardAbuseFemaleOnMale: Octavia's beating of her brother in 3x10 is framed in many ways as cathartic for the audience after Bellamy's actions in season 3a, but the incident (and the lack of stronger intervention by bystanders) would not have been accepted, much less celebrated, by the audience had their roles been reversed.

** The band of followers Jaha takes with him to find the City of Light. By the second season finale's end, only he and Murphy are still alive. This is acknowledged by Abby in season 3 when only Jaha returns.

* EarthThatWas: In the last scene of season 5, it is revealed that [[spoiler:Monty didn't think Earth would recover again from the ''Damocles'' strike in their lifetimes, so he redirected the Eligius ship to a new habitable planet. By the time the survivors wake up from cryo, they've been gone from Earth for 125 years.]]

** One of the significant differences between Clarke and Bellamy. Despite the above, Clarke is a more logical/necessity-based decision maker, while Bellamy tends to run more emotional/instinctive. She even refers to the two of them as people who think with their head and heart respectively. [[HourglassPlot Flipped around a bit]] in season 5, where Clarke points out that she's now the more emotional decision maker between the two of them.

** By the end of season 4 the StatusQuo of the first three seasons is broken completely. [[spoiler:Due to the Praimfaya wave all remaining twelve clans are forced to become one (called Wonkru) and 100 survivors from each clan band together to survive the radiation. Not only does this remove all of the individual clans from the equation but for the first time in Grounder culture the leader of their new people is no longer a Nightblood but instead a former member of Skaikru Octavia. Indra even {{lampshade}}s this noting that the time of the Commanders has passed.]]
** Done ''again'' at the end of season 5 -- this time, [[spoiler:the survivors -- Clarke and Madi, Bellamy and the characters sent to space, Wonkru, and Eligius -- ''aren't coming back to Earth at all'']].

** Season one: 29 days
** Season two: 23 days (followed by an 83 day time jump)
** Season three: 29 days
** Season four: 36 days (followed by a 6 year, 7 day time jump)
** Season five: 20 days (followed by a 125 year time jump, though the characters are unaffected due to the [[HumanPopsicle cryopods]])
** Season six: 11 days

* FantasyGunControl: The Grounders do not have any technology resembling firearms, not even primitive explosives. Season two reveals that this is enforced by the Mountain Men; they destroy the entire village of any Grounder who so much as touches a gun, so the Grounders live in superstitious dread.

*** TheLancer: Her {{Foil}}, Bellamy. Briefly replaced by her ShadowArchetype, Lexa, in season 2.

*** SixthRangerTraitor: Murphy in season 1. Lexa in season 2.

* FourLinesAllWaiting: The first part of season 2. By the fifth episode, they've converged.

** Computer screens throughout season four contain references to an Eligus Corporation and their deep-space operations, which foreshadows the Eligus ship that returns at the end of the season.

** At the climax of season two, Cage offers Lexa a deal: He will let all of the Grounder prisoners be released in return for her abandoning the Sky People. Lexa chooses her duty to her people--even though she's obviously in pain, and official commentary says she had genuinely fallen in love with Clarke.

** In season 4, Clarke is made to choose whether to save only her own people from Praimfaya, [[spoiler: a massive wave of radiation that will kill everything on Earth that isn't protected by a bunker]] and doom every single Grounder to death, or to save some Grounders and possibly cause the death of her own people. [[spoiler: She chooses to allow the Grounders to be wiped out, but Bellamy takes the decision out of her hands]].

* GreaterScopeVillain: Season One focused on petty squabbles between the 100 and the Trikru. Come Season 2, we are introduced to the Mountain Men, who the Grounders greatly fear, whose kidnapping of both Grounders and Skaikru forces a plot of cooperation between the Trikru and Skaikru leaders. Season 3 ups it again by introducing the ''murderous A.I. that started the nuclear holocaust in the first place'' against an increasingly fragile alliance among the clans. Season 4 tops them all by [[spoiler:focusing on [[AdvancingWallOfDoom the Praimfaya death wave]], which motivated ALIE's actions in the last season.]]

** The trope is downplayed in season two, as Monty is noticeably irritated that the budding romance between Jasper and Maya is driving a wedge between Jasper and Monty's old friendship.
* HairContrastDuo: Blonde, idealistic, caring Clarke with, well, pretty much everyone she interacts with at first, especially her more pragmatic mother and the older, moodier Bellamy. After she has made the damning moral compromises at the end of season two, her hair has been artificially darkened at the start of season three.

* HistoryRepeats: "Unity Day" in the first season revealed that the twelve space stations only came together to form the Ark after a thirteenth station had already been destroyed; in season three, the Arkadian settlement is offered a chance to join the Twelve Tribes in the Grounder coalition. Clarke explicitly states that they have a choice of either becoming the thirteen tribe or being the thirteenth station again. [[spoiler:The Arkadian leaders [[DefiedTrope defy a repeat of history and choose to join the coalition]]]].

* HumanResources: Season two reveals that the Mountain Men have used Grounder blood to treat their weaknesses to radiation, and in season two begin to harvest bone marrow from the Sky People as well.
* HumansAreBastards: Although the 100 initially believe that [[EverythingTryingToKillYou the environment will be their biggest challenge]], it quickly becomes apparent that the humans on the show are constantly at each other's throats, with progress towards peace always getting derailed. This is part of why [[spoiler:Jasper decides to kill himself, having given up on humanity.]] Monty calls back to this in the season 5 finale, asking Clarke and Bellamy to defy this now that [[spoiler:the survivors have been given a second chance on a new planet.]]

** In season 5, when the soybean crops die, it's [[spoiler:not just cannibalism but ''forced'' cannibalism, on penalty of death, that is what gets Wonkru to survive. No wonder they call it the Dark Year.]]

** In season 5, Bellamy tells Clarke, "That's not my sister" after seeing how the bunker has changed Octavia. After she [[spoiler: puts him in the fighting pit and sentences him to death,]] he outright tells her that he wishes she were dead. Later, during the march to Shallow Valley:

* IKnowYouAreInThereSomewhereFight: When Bellamy sides with Pike over Kane, Clarke believes that if she can reach him she can convince him that peace with the Grounders is the best option. She pleads with him not to turn into somebody who believes that war is the better option and to work together to find a solution for everybody. Bellamy refuses her call, claiming this is who he always ways, and that his better actions with Clarke and Octavia were when he was acting out of character. Double-subverted in the back half of season 3, where he admits that he regrets his actions and now has to live with the consequences.
** Bellamy has a similar conversation several times with Octavia throughout season 5. She tells him, [[spoiler: "You can't save someone who's already dead."]]
** Clarke crosses this with StopOrIShootMyself in the Season Six finale. [[spoiler:When she sees that Sheidheda has taken over Madi’s body, she threatens to shoot herself if Madi can’t take back control. It works just long enough for Madi to order Russell taken hostage, at which point Sheidheda starts [[BattleInTheCenterOfTheMind killing her from the inside]].]]

** There's another one at the end of season 4 after a TimeSkip. [[spoiler:Clarke, in a daily transmission to Bellamy, lays out the state of the world after Praimfaya, though she's aware that she might be talking to no one.]]
* IntergenerationalFriendship: Murphy and Jaha on their journey in season 2. They do grow closer, but it's also happening in the middle of Jaha's SanitySlippage, and their friendship quickly sours.
** [[spoiler:Octavia and Diyoza also bond to some degree in season six, after admitting to being NotSoDifferent and both had been exiled from Sanctum.]]

* InternalDeconstruction: Season 5 reverses the dynamic of Grounders vs. Sky People, with the protagonists on the ground and a new group of criminals as the colonists from the sky. Many of the same beats are repeated, but with characters are much more experienced and try to make different choices, and recognize why their choices in season 1 were moronic or foolhardy.

* KarmicDeath: In the finale of season two, Cage dies from the very drug he used to turn Grounders into Reapers, ''and'' the very syringe he was about to inject Lincoln with. The event even comes with an IronicEcho.

** Done in season three when Nia, the Queen of the Ice Nation, has challenged Lexa's authority as the Grounder Commander. When she selects her son Roan to fight Lexa in TrialByCombat, Clarke approaches him and tries to persuade him to kill his mother instead and thus become King. Roan considers it, [[SubvertedTrope but declines because he knows that the Ice Nation would never forgive him or accept him as their King in that situation]]. [[DoubleSubverted He does, however, offer to help]] ''[[DoubleSubverted Clarke]]'' [[DoubleSubverted kill her instead]]. [[spoiler:Nia survives Clarke's assassination attempt, but during the fight between Lexa and Roan, Lexa spares Roan and kills Nia on the sidelines. She then declares Roan King of the Ice Nation]].

** Hope turns up in the last minute of season 6.

** As of season 3, [[spoiler:Emerson, Last of the Mountain Men, is the SoleSurvivor of the people of Mount Weather]]. But subverted when he dies later making his people officially extinct.
** After [[spoiler:Ontari's]] death in the penultimate episode of season 3, [[spoiler: Luna]] remains the last known living [[spoiler: Nightblood]], but it is implied that there may be others in other villages and clans.

** From the season two finale, "Blood Must Have Blood, Part 2":

*** Bellamy tells Clarke that if she wants forgiveness for irradiating Mount Weather and killing everyone inside, he's willing to forgive her -- a direct parallel to their conversation in "Day Trip" where Clarke forgives him for indirectly causing the Culling. When Clarke refuses, she says "I bear it, so they don't have to", the same thing President Wallace said to her earlier in the episode. This phrase pops up again in season 4, when Clarke injects herself with the Nightblood serum instead of a restrained Emori.
** The final climactic moments of seasons 2 and 3 both involve Clarke pulling a handle.
** Kane's ultimatum to Abby in season 5 to either quit taking the pills or lose him ends with the single word "Choose" - just like Octavia's message to possible enemies of Wonkru.

* MedicalHorror: The terror of the final episodes from season two comes from the Mountain Men harvesting bone marrow from the 100, cutting them apart and draining them dry.

** Raven, when she realizes that A.L.I.E's way of "removing the pain" means she no longer remembers the feelings she had for Finn and how much he meant to her. [[spoiler:In season 7, to stop Sanctum's nuclear reactor from exploding, Raven sends in several convicts to effect repairs, and they all die from radiation exposure. She bitterly regrets not taking the time to come up with a non-lethal solution, especially since she ignored that EvenEvilHasLovedOnes.]]
* MySisterIsOffLimits: In the beginning of season 1, Bellamy tries to stop his younger sister from flirting with any of the people on the Ground, specifically Finn.

* TheNeutralZone: [[PlayingWithATrope Played with in season three during the conflict between the Grounders and Arkadia]]. Lexa wishes to prevent an all-out war between the two people, but cannot allow Arkadia's repeated acts of aggression to go completely unanswered, so she enacts a five-mile quarantine surrounding Arkadia. She will not allow the Grounder armies to attack the settlement, but any Arkadian who leaves the boundary will be killed.

* NoPeriodsPeriod: The lack of the 100 dealing with any menstrual cycles while stranded on the ground without any supplies is explained in season three: Fertility inhibitors prevent both pregnancy and menstrual cycles, and people discuss removing them at the start of this season.

** Foreshadowed and implied throughout the beginning of season three, "Thirteen" reveals that the Grounders and the Sky Crew have a historical connection leading back the formation of the Ark and the First Commander.

** Also happens with Eliza [[spoiler:playing Josephine]] in season 6. After the scene in her room, however, she seems to have it back under control.

* PlatonicLifePartners: Lead characters Clarke and Bellamy form a balanced partnership in season one that is as often deepened as it is strained by the events of the show. While they both have multiple love interests, their relationship is often front and center, they frequently forgive and support each other, and both consistently admit that the other is hugely important to them, to the point that they are occasionally implied to be each other's LivingEmotionalCrutch. Despite all this they don't get romantic, although there are quite a few ShipTease moments.

** As a consequence of the events of season 2, the Grounders take to calling Clarke "Wanheda", which means "The Commander of Death". Another epithet that she gains is "Mountain Slayer".
** In season 4, the Grounders begin calling Octavia "Skairipa", meaning "Death from above", because of her growing infamy as a killer. By the next season she's moved on to [[spoiler:"Blodreina", meaning "red queen", as leader of the bloodthirsty Wonkru]].

* RememberTheNewGuy: Season three introduces a few new characters in the time skip, whom the core cast are already familiar with as friends or family from back on the Ark.

* SanitySlippage: Ooh boy, the setting is not good for mental health. Clarke, Jaha, and Finn all struggle with it in season 2. Murphy has a hard time after being alone for 80 days in the third season. Season 5 shows Octavia, and to a lesser extent all of Wonkru, becoming pretty crazed.

* SequelEscalation: The stakes get higher with every season. While season one focuses on the delinquents dealing with a few Trikru authorities, season three features an interclan war, and season four is about the cast trying to survive ''yet another apocalypse''.

** In the beginning of season three, Clarke sleeps with Niylah as part of her ongoing efforts to cope with her guilt and despair over the end of season two.

** Bellamy is implied to have kept the trauma he underwent in Mount Weather mostly to himself in the TimeSkip between Seasons 2 and 3. This coupled with [[spoiler: several Skaikru deaths in Mount Weather, including that of his girlfriend Gina]], and Clarke's perceived betrayal by allying with Lexa, causes him to [[AntiVillain support Pike]], which, in turn leads to a huge MyGodWhatHaveIDone moment. By season 4, he doesn't think [[spoiler: that he deserves to be one of the people who deserves to be in the ship when the radiation comes and has a desperate desire to redeem himself before the end comes.]]

** Clarke is haunted by the increasingly horrifying things she does to protect her people, and she goes a bit nuts when this tendency comes into conflict with her newfound MamaBear instincts for Madi. By season six she's nearly convinced that everyone would be better off without her, and is nearly DrivenToSuicide on three separate occasions.
** Partially subverted in season 7, in which Jackson (normally a medical doctor) starts acting as a therapist for Madi.

** The back half of season two alternates between the Mount Weather crew and the rest of the Sky People trying to find a way to save them, but adds Jaha and Murphy's quest for the City of Light to the mix. It's geographically removed (as it's them trekking across unfamiliar terrain) and has little in common with the other two plots...until the season two [[TheStinger stinger]].

** Season 3 starts precisely 84 days after the events of the season 2 finale.

** The Season one finale sees both regular sets utterly destroyed: The Ark is brought down, and the Hundred's camp is thoroughly incinerated.
** [[spoiler:Mount Weather gets blown up early in season 3.]]
** By the end of season four, [[spoiler:both Arkadia and Polis are destroyed by Praimfaya. The rest of the world is presumed to be in a similar state.]]
* TragicMonster: The cannibalistic and savage Reapers turn out to be a whole tribe of these. Season two reveals that they are former Grounder captives, who due to being physically fit were turned into Warrior\Slaves by Mount Weather experiments to be used as both weapons, hunters and gatherers against their will.
* TrialByCombat: At the start of season three, Lexa's position as Grounder Commander is tenuous due to her perceived weakness. Nia, Queen of the Ice Nation, challenges her authority, naming her son Roan as her champion. Lexa also has the legal right to a champion, but since the underlying point is that her strength is in question she chooses to face the challenge herself. [[AuthorityEqualsAsskicking She wins]].

** Marcus Kane starts the series as next in line for the position of Chancellor on the Ark, and when it looks as though he will succeed Jaha Abby fears he would be disastrous for the people. However, [[SubvertedTrope despite several near-deaths on Jaha's part, Kane never succeeds him during the first season]]. [[DeconstructedTrope By the time Kane does become Chancellor in season two he has undergone enough character development where he is no longer even a potential Tyrant.]]

* VillainHasAPoint: In season three, Clarke and Bellamy are arguing about the oncoming war between Arkadia and the Grounders. During the argument, Bellamy points out the moral and practical errors that Clarke had made which lead them to that point. Instead of countering the argument, Clarke can only apologize in tears, because she has also made mistakes.

* WhatHappenedToTheMouse: The first season featured quite a number of mutants, both human and animal alike. A two headed deer featured prominently in promotional material. By season 3, they virtually never appear in any capacity, aside from Emori.

* BornAgainImmortality: The Grounders believe this is what happens to the Commander: when they die, their spirit chooses the next Commander, who emerges as the winner of the battle royale–esque Conclave. "Thirteen" reveals that [[spoiler:the Commander's spirit is really the A.L.I.E. 2.0 chip, also called the Flame, which is implanted in each Commander's brainstem and passed on from one Commander to the next.]]

** Season 7: [[spoiler:Bellamy, Diyoza, Russell and Nelson.]]

** Season 7: [[spoiler:Bellamy and Diyoza.]]

* AnyoneCanDie: The series has killed off several supporting/minor characters and so far one main character per season and also isn't shy about high body counts even including children. The notable deaths per season are:

* CultColony: Sanctum. It wasn't ''meant'' to be one; at least a couple of the original colonists were staunch atheists. But when the Primes discovered a form of {{Immortality}} by uploading their [[BrainUploading Mind Drives]] into [[BodyBackupDrive new host bodies]], they started raising all future generations of the colony in a cult that worshipped the Primes, [[RaisedAsAHost grooming them to willingly give up their bodies for the Primes' use.]]

* BadassGay:
** Lexa, who is introduced as the Commander of all the Grounders and just so happens to be a lesbian.
** Clarke is revealed to be a BadassBisexual in season 2.
** Miller, who is confirmed to be gay in season 3.

One hundred juvenile delinquents are sent down to Earth in a dropship to see if it is survivable. Cut off from the Ark due to a landing mishap, the delinquents try to set up camp on the ground. But while the group's eventual leaders -- Clarke Griffin (Eliza Taylor), a privileged young woman who was kept in solitary lockup because of the secret her father was killed for knowing, and Bellamy Blake (Bob Morley), a rebellious former guard demoted after the Ark learned about his illegal younger sister Octavia (Marie Avgeropolous) -- find that establishing a functional society comprised of teenagers on an unfamiliar planet is hard enough by itself, there's one other major complication: they aren't the only humans on Earth. The camp quickly comes into conflict with the Grounders, clans of people who also survived the apocalypse, and who aren't happy about the 100 crashlanding onto their territory.

On the Ark, its leadership scrabbles to maintain order. Clarke's mother Abigail (Paige Turco) alternately clashes and cooperates with fellow councilor Marcus Kane (Creator/HenryIanCusick) and the Ark's leader, Chancellor Thelonius Jaha (Creator/IsaiahWashington), as they try to stay on top of the Ark's ever-growing list of problems.

* RaceLift: Implied as much; in the books, Wells is half-brother to the Blake siblings, but this is unlikely in the show given the actors' ethnicities [[note]] Eli Goree (Wells) is black, Bob Morley (Bellamy) is half-white, half-Filipino, and Marie Avergopoulos (Octavia) is white[[/note]].

*** Octavia's eligibility for both the historical and sci-fi name themes might be a nod to her dabbling in both cultures.

** Partially subverted in season 7, in which Jax (normally a medical doctor) starts acting as a therapist for Madi.

** Clarke works with Anya to escape Mount Weather in "Reapercussions," and despite their conflict throughout the escape Anya agrees to propose an alliance to the Grounder Commander against the greater danger of the Mountain. Anya is mistaken for an attacker by Ark security personnel and killed before she can do so.

* FakingTheDead: Removing the wristband monitors makes the wearer appear to be dead as far as the people back on the Ark know. After the landing, Bellamy wants to make it appear that The 100 all died so the Ark won't send anybody else down, leaving them free to live by their own (lack of) rules. After realizing that this was a ''terrible'' idea and learning that the Ark is going to have another culling soon due to the ground apparently being confirmed inhabitable, it's a race to signal the Ark that they're not dead.

* FelonyMisdemeanor: Due to AllCrimesAreEqual on the Ark, the tiniest misdemeanor is the same under the law as cold-blooded murder. However, although they are punished equally by the law, society hasn't come to view misdemeanors as death-worthy offenses and instead resents the laws, at best accepting them as a brutal necessity.

** In season 4, Clarke is made to choose whether to save only her own people from Praimfaya, [[spoiler: a massive wave of radiation that will kill everything on earth that isn't protected by a bunker]] and doom every single Grounder to death, or to save some Grounders and cause the death of her own people. [[spoiler: She chooses to allow the Grounders to be wiped out, but Bellamy takes the decision out of her hands]].

* IntergenerationalFriendship: Murphy and Jaha on their journey in season 2. They do grow closer, but it's also happening in the middle of Jaha's SanitySlippage, and their friendship soon sours because of this.

** Raven, when she realizes that [[spoiler: A.L.I.E's way of "removing the pain" means she no longer remembers the feelings she had for Finn and how much he meant to her.]]

** Raven deals out {{Breaking Speech}}es in this form in "Nevermore," calling out Clarke and Bellamy for all the deaths they've caused and Jasper for being incapable of moving on.

* RoyalBlood: Some Grounders have [[AlienBlood black blood]], for which they are termed "Nightbloods". Grounder tradition has the Nightbloods identified as potential successors to the Commander, and one of them will arise to the position with the death of the current Commander.

* SelfHarm: After [[spoiler:A.L.I.E. possesses Raven]], she forces her host to make deep gashes along her arms.

** In the season finale, one of the 100s shout "[[Film/{{Aliens}} Game over, man!]]"

** Season 3 begins with Clarke trying to negotiate peace in Polis, Bellamy, Kane, Abby at Arkadia dealing with Pike's politicking, and Jaha's own City of Light related plot.

** Clarke to Finn after [[spoiler: he, usually the pacifist of the group, snaps and slaughters a large number of innocent villagers]]. Everyone else is clearly thinking it as well, but don't come out and say anything.
** Raven to Clarke after [[spoiler: Finn is mercy-killed. This is mostly due to Raven's grief, as she later realises there was no other way.]]

* WorldOfSnark: On a planet populated entirely by teenagers, this is pretty much a given.