Lancelot

As a child, Lancelot is raised near a lake by his mother, a powerful woman known as the Lady of the Lake. ("Lady of the Lake," "Broken Heart")

In Camelot, Lancelot travels with Percival and Arthur to track down the sword in the stone after Merlin prophesies that Arthur will pull it out and become the ruler of the realm. They are beaten there by Sir Kay, who foolishly tries to take the sword out, only to be turned into ash by the sword's power. As Lancelot and Percival look on, Arthur succeeds in pulling out the sword, but strangely, the tip of the blade is missing. Arthur momentarily panics at this, but he then decides the kingdom's people don't need to know about it, and that all they need to know is he is now their king. ("The Dark Swan")

Afterwards, Lancelot and Percival return home with Arthur, who is met with fanfare by the local villagers in celebration of his ascension. Sometime after becoming king, Arthur bestows the Round Table's Siege Perilous seat, which is only fit for a knight with the purest heart, to Lancelot. ("Siege Perilous," "The Broken Kingdom")

During his reign as king, Arthur becomes consumed with finding the missing piece of Excalibur, Dark One Dagger, while neglecting his wife Guinevere, who tries to coax him away from his research to dance with her on her birthday. During the party, Lancelot notices her sitting alone and joins her, trying to reassure her that Arthur will be arriving soon. While Guinevere is dancing with Lancelot, a fellow villager announces Arthur has prepared a surprise for his Queen, before showering flower petals into the air. At first, Guinevere is pleased, until she realizes Arthur didn't prepare anything, and it is Lancelot who wanted to make her happy. For this, she thanks him, shortly before they are interrupted by Arthur rushing to them, exclaiming that he discovered the dagger is only a day's ride away. Assuming he will be the one going, Lancelot prepares to get his horse for the journey, but Arthur asks him to stay and protect Guinevere, while he himself will go. That night, Lancelot catches Guinevere trying to leave on her own, as she found the true location of the dagger with a Magic Gauntlet, which revealed the dagger as Arthur's greatest weakness. Lancelot accompanies her there, and the gauntlet takes them to the Vault of the Dark One, where Guinevere unlocks a staircase into it. In the vault, Lancelot is attacked by the Darkness, but Guinevere scares it off with fire. Relieved to have not lost him, she kisses him in the heat of the moment, before apologizing and stating that it can never happen again. From one door, they enter a jungle-like region and find the dagger on a table stand, but it's protected by a barrier. In exchange for the gauntlet, the Dark One offers Guinevere magic sand that will give the illusion that Excalibur is whole. Lancelot begs her not to, but Guinevere accepts the deal. On their return to the village, Lancelot bids her farewell, deciding to leave Camelot forever, knowing that she has chosen Arthur over him. ("The Broken Kingdom")

Afterwards, Lancelot comes to the Enchanted Forest, becoming King George's new general, and aiding him with hunting down Prince Charming. During a battle, he captures Snow White and brings her to the King. Upon order by King George, he fetches Snow White a cup of water. The water curses Snow White to be barren forever, and unable to bear any children. Afterwards, she is let go, but Lancelot follows her into the forest. Snow White is furious, and attacks him. He begs her to spare him because he, too, was unaware of the poison the king put into the cup. She allows him to come with her, and together, they return to Prince Charming and his mother, Ruth. The king's men have them surrounded by the time they reach back, and worse yet, one of their poisoned arrows has struck Ruth. Prince Charming suggests they go to Lake Nostos and gather some of the lake's waters, which has healing powers. When they reach there, they find the lake completely dry, except for a few droplets of water left. However, Ruth only pretends to drink the water, and as her dying wish, she asks to see her son and Snow White married. During the ceremony, Lancelot fills a cup with the lake water, stating that in Camelot there is a legend of a cup and it's believed whoever drinks from it will become immortal. Snow White drinks it, and after the marriage is complete, Ruth passes away. Afterwards, Snow White discovers she is no longer barren and figures out Ruth must have given the water to Lancelot to put in the cup. ("Lady of the Lake")

Sometime after the first curse is cast, Cora begins glamouring herself as Lancelot, helping to manage a refugee camp for survivors that were not taken by the curse. Mulan becomes one of his allies at the haven, and Cora pretends to be held as a prisoner there because of her association with the caster of the curse. When Mary Margaret and Emma end up stuck in the Enchanted Forest, Lancelot immediately recognizes Mary Margaret as his old friend Snow White and agrees to help them figure out a way home. With Mulan, and later Aurora, the women head to the old royal castle to look for the magic wardrobe. Lancelot appears before Mary Margaret and Emma, explaining that he followed them to ensure their safety and how they will get home. Mary Margaret senses something is amiss when Lancelot mentions Emma's son Henry since Cora is the only one in this world who knows about him. When Mary Margaret calls her out for this, Cora emerges from the facade, claiming that Lancelot is dead and she had killed him long ago since the refugees would have never listened to her. After a brief scuffle, Cora is forced to retreat. Mulan is aghast that she was tricked by Cora's disguise for so long, while Mary Margaret persuades her to tell the survivors that Lancelot died an honorable death. ("Lady of the Lake," "The Doctor")

Somehow, Lancelot deceived Cora and remained alive, though how he survived is not known. At some point, he returns to Camelot and sneaks into King Arthur's castle. During the night David is bestowed the Siege Perilous seat by Arthur, Mary Margaret goes out to the hallway to calm down her crying baby son, where she sees a shadowy figure walk past. When she calls out to the person, Lancelot steps out, much to her astonishment. He assures her it is truly him, and after putting aside the story of his struggles, he warns her about a villain that is currently in the castle. At first, Mary Margaret assumes he is speaking about Emma, who is now the Dark One, but instead, Lancelot reveals Arthur is the villain and Camelot is not what it seems. ("Siege Perilous")

To keep his return a secret from everyone else, Mary Margaret brings Lancelot to the diner, where he stays until she comes back with the Dark One Dagger, asking his help to hide it from Arthur. As he leads her to the Vault of the Dark One, Mary Margaret asks him about his past with Guinevere. Lancelot avoids getting detailed and simply says it no longer matters, while she reasons it must if he still loves her. To this, he admits he still does. After they enter the vault and travel into the jungle room, Lancelot cautions Mary Margaret against putting the dagger on the table stand since it has a barrier. When she insists on trying, he tries to persuade her into letting him do it instead. Upon seeing her hesitation, Lancelot questions if she doesn't trust him, but before she can answer, Arthur arrives, having followed them. Arthur threatens to kill Lancelot unless Mary Margaret gives him the dagger, and after he moves to make good on his threat, she finally hands it over. While relishing in his victory, Arthur tries to summon Emma, only for it to fail, as Mary Margaret admits the dagger is fake, before David corners him from behind. Lancelot, David and Mary Margaret take Arthur to the diner, where the trio make plans to install Guinevere as the new ruler of Camelot, but suddenly, they are ambushed by Camelot soldiers led by Guinevere. Realizing she is under the the magic sand's influence, Lancelot attempts to talk her out of helping Arthur, but she takes back Excalibur and orders the guards to take him to the dungeon. Thrown into a cell, Lancelot quickly becomes acquainted with another prisoner, Merida, who suggests they can be allies since Arthur is their common foe. ("The Broken Kingdom")

Still imprisoned, Lancelot is quickly rescued by David, Hook and Belle with Merlin's help. After Merlin magically obliterates the prison bars, Lancelot and Merida escape the dungeon with the group. ("The Bear and the Bow")

After Emma turns Hook into a Dark One, Lancelot and the others go to the Vault of the Dark One to find Hook, but they find him already gone. With time running out, Lancelot is sent off to his mother, the Lady of the Lake, who might be able to help them, though the journey will take him two days to get there. ("Broken Heart")