Gaia was born on Earth and is the daughter of Indra. Indra trained her to be a Trikru warrior and leader, but then Gaia chose to dedicate herself to the sacred flame and become a scout for the Flamekeeper, searching the land for nightbloods.
In Echoes, Gaia is in the crowd when Roan announces that he will be the Keeper of the Flame until the next Commander can be found. She yells at him that he is not a priest and that this is blasphemy.
In The Four Horsemen, Roan asks Octavia to track down and kill the person who stole the Flame from him. Octavia tracks down Gaia and corners her in the temple. The two briefly fight, until Octavia gets the upper hand. Just before Octavia goes for the kill, Indra calls for Octavia to stop. When, Ilian and the looters come to the temple seeking to destroy the Flame. Octavia and Gaia come up with a place to save the flame.
In 'The Children of Gabriel', she is sitting on the door of the Gagarin with Madi and Diyoza. She is trying to get Madi to master the flame but, Madi fools around and says that she sees Clarke Griffin needing her help. Gaia says that's impossible, because Clarke's mind left the flame with she left the City of-. Then Gaia realizes that Madi is not being serious and gives up. Madi the tells her about seeing a commander with scares on his face like lines on a map and wearing all black and that she tries to ignore him. Gaia, shocked, tells Madi that is "Sheidheda" or the Dark Commander and that Madi is right to ignore him. Diyoza the laughs at the two. Gaia stands up and says "Why's it funny?". Dioyza responds it's not, it's sad. Dioyza then quickly stands up pulls out a knife, Gaia thinks Diyoza's going to hurt her and Madi, but she throws the knife into a child of Gabriel. The three are then attack and paralyzed by parlyptic darts.
In The Gospel of Josephine, Josephine, pretending to be Clarke, enters the room where she meets Madi and shocks the group by suddenly allowing her to go to school. Speaking in Trigedasleng, Gaia questions "Clarke's" sudden change of mind as it risks exposing Madi as a Nightblood. Luckily, Josephine doesn't understand Trig and therefore doesn't figure out Madi is a nightblood.
Later, she help Jordan to find the truth about Primes, they sneak up to the room filled with skeletons where they meet up with Bellamy, Murphy and Josie. Gaia notices that the skeletons have the Flame infinity symbol and wonders if they were all Commanders. Bellamy figures out that the skeletons belong to the original Eligius IIIMission Team Alpha. He notices that some of the skeletons belong to kids; and Josie explains that people will do anything to ensure survival for the ones they love. Josie starts urging them to respect Sanctum traditions and leave but Jordan continues exploring. He finds a secret door which leads to a lab.
In the lab, they notice a lot of Becca and Flame-related technology. Bellamy explains that they can't be commanders because Becca didn't invent the Flame until after the first apocalypse. However, she provided her technology to Eligius Corporation before then. Jordan finds a computer and unlocks it using the Eligius III access code. They find a list of video logs. Gaia suggests playing the one titled "Eureka!".
On the video a doctor named Gabriel Santiago is forcibly experimenting on a young woman named Brooke. Josie's old dad is by Gabriel's side, encouraging him. Gabriel explains that they needed to use a fully developed brain and clear the host's consciousness first in order to accommodate the full memory size. He takes out a Mind Drive which looks a lot like the Flame. He knocks Brooke unconscious and inserts the Mind Drive inside her neck. A few moments later, Josie wakes up violently inside Brooke's body. She is proud of Gabriel for reverse-engineering the Mind Drive technology to be able to upload an entire mind into a new host. Gabriel ends the experiment by saying that Josephine was the first success, with more to come.
After watching the video, everyone is horrified by the inhuman experiments they just witnessed. They figure out that the Primes have been manipulating nightbloods to sacrifice themselves to false gods. Jordan calls it murder, but Josie claims the hosts were willing even though Brooke was forced into it. Murphy is indifferent, claiming that back on Earth, he points to Gaia that they used to arm kids to go to war. Realizing that Madi is in danger, Gaia says she will go get her back from school. This helps Josie figure out that Madi has royal blood. She offers to come along.
Later at the bar, Gaia, Bellamy and Jordan are surprised that Clarke seems to be willing to tolerate the Primes' actions. Gaia calls the Primes out for abusing Becca's Flame technology whose intended purpose was to pass wisdom from one person to another. Instead, the Primes want to keep all the wisdom to themselves. Murphy disagrees with her, saying that Becca was just a scientist who was turned into a nightblood in a lab - the same way Abby did to Clarke. This makes Josie realize that it is possible to turn ordinary people into nightbloods.
Gaia is very devoted to the Grounder faith. She chooses to follow her faith instead of becoming a warrior like her mother, Indra. Later, she risks her life by stealing the Flame because she believes it is blasphemy for someone who is not an ouspika (priest) to be the Keeper of the Flame.
Indra: "My faith is not as pure as yours, but you are as responsible for what Octavia became as I am. Blodreina was a leader we needed then. We need a true Commander now. Will you do it or not?"
Gaia: "The decision isn't mine to make. The child must choose for herself."
-- Sic Semper Tyrannis
She was originally meant to have a bigger role in Echoes, but her biggest scene was cut. In the scene, she was riding a horse when she came across Ilian in a forest (who had already killed his brother in the original episode's opening). They conversed about A.L.I.E.'s chip, his family being dead, and wrapping them in cloth.
Gaia and Madi are the only two characters that were introduced in Season Four who are known to be alive.