<P> In "Bitter Harvest," Lexa worries that by trying to make peace instead of engaging in war, she is betraying the commanders who came before her . Clarke assures her that her legacy will be peace . Roan has Emerson, the last Mountain Man, delivered to Clarke; she must decide his fate . She ultimately decides to let Lexa banish him . </P> <P> In "Thirteen," the Grounders celebrate their Ascension Day, a holy day for Grounders . Octavia and a man named Semet walk in claiming the Sky People destroyed their village . Discussing the situation, Titus wants Lexa to destroy the thirteenth clan while Clarke thinks they just need time to take out Pike from the inside . Speaking to everyone, Lexa orders the armies not to attack, but instead make a perimeter around Arkadia and says that any Sky Person found past the five mile buffer will be killed . Semet is angry at this and attempts to kill Lexa, but is stopped by Titus who kills him . Later, Titus is against Clarke staying, believing she further endangers Lexa's life . He warns Lexa that, just like with Costia, she may not be able to separate feelings from duty . Lexa is enraged at this, reminding him that because she let Ice Nation into her coalition even after they cut off Costia's head and sent it to her bed, she is more than capable of separating feelings from duty . Later, Clarke goes into Lexa's room and realizes she is saying goodbye . Clarke says the reason she is going back is because the Sky People are her people . Lexa says that this devotion is what makes Clarke the person she is . Clarke suggests that maybe someday they will owe nothing more to their people, and Lexa responds with "May we meet again ." Clarke kisses her and they have sex . Afterward, Clarke admires Lexa's tattoos, pointing out there are only seven circles on her back despite there being nine participants . Lexa tells her she got the one on her back on her Ascension Day, and asks to talk about something else . Clarke agrees and they become intimate again . </P> <P> It is later, as Lexa is running into Clarke's room, that Lexa is accidentally shot by Titus, who intended to kill Clarke . Clarke catches Lexa as she falls and they take her to the bed . Lexa realizes she is going to die and tells Clarke not to be afraid . She tells Titus to never harm Clarke again, and he swears he will not . She tells him serve the next commander as he served her . Clarke continues to try and save Lexa, but she tells Clarke that her spirit will find a new commander . She says her fight is over and that Clarke was right that life should be about more than just surviving . Clarke recites the Traveler's Blessing, an Arkadian prayer . As Lexa dies, Clarke kisses her one last time . Titus extracts a tech from Lexa's neck, where her tattoo is . The tech is called "the flame," and it is revealed to be Lexa's spirit . She was augmented to carry an AI (the flame). The flame is how every new commander is chosen, with each new commander becoming a part of the flame . It is only compatible with Nightbloods . Aden is meant to succeed Lexa, but, in "Stealing Fire," he is murdered by Ontari, a rogue Nightblood who seeks the throne for herself . </P> <P> In "Perverse Instantiation--Part Two", Clarke is on a mission to stop a holographic AI named ALIE from world domination . ALIE is the one responsible for launching a nuclear strike on Earth because she believed it was needed to save humanity from extinction . This is in contrast to what her creator, Becca, had wanted . With Jaha's help, ALIE has been successful in getting many of the Sky People to swallow a chip that takes away pain (emotional or physical) and simulates a utopia called "the City of Light ." In this city, those who have died live on . ALIE uses this chip to entice and control people . Clarke had tried to get Luna, a missing Nightblood and rightful heir to the Commander throne (as indicated by the tattoos on Lexa's back), to accept the flame, but she refused . Clarke is implanted with the flame with the help of a blood transfusion via a brain - dead Ontari, whose blood is compatible with the flame . Clarke takes one of ALIE's chips and enters the City of Light to stop ALIE from within . She is protected by Lexa's spirit and aided by Raven's hacking against ALIE's minions, leading her to a room resembling the Polaris space station, where Becca's spirit shows her the kill switch to destroy ALIE . Before Lexa sacrifices herself to get Clarke to safety, Clarke tells her that she loves her . Lexa says that her spirit will always be with Clarke . </P>

What season did lexa die in the 100