Margrethe is a former slave, and now a free woman, resident in Kattegat. As a slave, she had affairs with all four sons of Ragnar and Aslaug simultaneously but now as a free woman she is married to Ubbe who now refuses to share her anymore with his brothers. However, Ubbe is lovers with Torvi, his half-brother's former wife.
Margrethe is a young teenage slave owned by Aslaug; her sons (apart from Ivar) all use her as a shared lover, something that Margrethe seems content with. She is first seen having sex with Ubbe inside a barn, while Ivar secretly watches. Smiling and satisfied, Ubbe asks for her name, which she provides, returning her answer with a small chuckle. Ivar continues to watch her as she has passionate sex in the forest, first with Hvitserk, then with Sigurd.
Jealous, Ivar speaks to his brothers about losing his virginity to the same girl; Hvitserk replies that he can have sex with any slave he likes, while Ubbe insists on asking her since she is still a person and not livestock.
Ivar gets his wish and the brothers procure Margrethe to have sex with him, leaving an insecure Ivar alone in bed. Margrethe approaches Ivar and tells him not to be afraid. She kisses him and he hesitantly kisses her back before lying on the bed, naked. She pulls up the blanket that covers his deformed legs and off her clothes and sits on top of him, exchanging small kisses. Ivar attempts to be on top of her, her small cries indicating that she's not enjoying it. Unfortunately for Ivar, he is unable to complete the act and lays beside her, angry. Ivar then pulls himself above her back and tries to strangle her with a cord, stating he has to kill her for fear she will tell his brothers about what happened.
Pleading for her life, she tells Ivar that she'll always speak about his virility and that she will blame herself for not enjoying their intercourse. Ivar is not interested in that since he enjoys killing and she's only a slave. Margrethe, choking tells Ivar that he's right, that nobody will care except the gods, who will know the truth. Intrigued, Ivar pulls away and Margrethe explains that "[the gods] will laugh at you for being such a coward. So your prick doesn’t work. Does that make you less of a man? No, it doesn’t. Lots of men can have sex. Lots men can have children. Those things are easy. To be a son of Ragnar Lothbrok and to find greatness that is hard. I truly believe that". Ivar grabs her hand and sobs in front of her.
Later, Sigurd asks how the encounter went. Shaking in fear, Margrethe says that he's the most brutal man she's ever met and that he almost killed her. When Sigurd asks her why he wanted her dead, she tells him the truth (Ivar didn't want anyone to know about his inability to satisfy women sexually). Sigurd chuckles and Margrethe begs him to not tell anyone, which he quickly does, by telling Hvitserk and Ubbe soon after.
The next day, Margrethe serves breakfast to Aslaug and her four sons. She hesitates to approach Ivar, who notices that she is uncomfortable and smirks at her and begins to grope her while being served. Ubbe tries to intervene, telling his brother off for treating her like that, though Ivar quips that she's just a slave. Taking Ubbe's side, Aslaug tries to correct her son's behavior but finds herself unable to scold him. Margrethe is ordered to sit beside Ivar, helping him eat his food and acting as if they were a couple. Ubbe and Hvitserk start to laugh at him and his pretend wife, knowing he could never satisfy her (or any woman). Angry, Ivar asks them why they're laughing at him since he now has a special servant and that she has many reasons to be grateful to him. Hvitserk says that he can't keep a slave to himself like that, and Ivar mocks his older brother by asking his mother to tell him to stop tormenting him. Aslaug, bored, replies by saying that she's happy to see Ivar with a woman and tells her other sons that all of them should already be married and that it is important to find a woman and settle their lives. Sigurd quips that he thought he had found the woman, but Ivar took her away from him. Aslaug is unimpressed with the notion and tells Sigurd he deserved a better woman to make children with which starts a fight about having a relationship for love rather than status.
Confused, Ivar lets go of Margrethe's hand and he asks his brother what was wrong with him. Sigurd answers that nothing is wrong with him, but that everyone only pities him, including their mother. Aslaug calls out for Sigurd for his remarks, and Ivar, enraged, tries to attack his brother. He is unsuccessful because of his disability, which only angers him more. Margrethe sees everything, horrified for Sigurd since she knows what Ivar is capable of.
During the night, while she's sleeping, Ivar crawls to her, quietly, and pokes her cheek, waking her up. She's startled by his sudden appearance but Ivar manages to quiet her by putting a hand over her mouth. He then says that she told Sigurd about their time together, and Margrethe begs she didn't say a word. Ivar first says he doesn't believe her and threatens to strangle her when he moves his hand to her neck. Margrethe swears she didn't tell anything to anyone and Ivar lets go of her and hushes the slave, saying he believes her and asks for her to let him lie next to her. Ivar sleeps peacefully next to her, while Margrethe remains awake, unable to rest beside her attacker.
Sometime later, Margrethe is brought to Hedeby by Torvi, where she meets with Lagertha and Astrid. The younger shieldmaiden asks about Margrethe and Torvi reveals that she is a slave who was being used by Ragnar's sons. Shocked and curious, Astrid asks if all the brothers have used her and Margrethe nods. Torvi then asks her if she hates them, but Margrethe doesn't have any ill feelings towards the brothers, apart from Ivar.
Ubbe and Sigurd are invited to Hedeby where they eat with Lagertha, Astrid, and Margrethe. When Ubbe inquired upon the invitation and why their slave is there, Lagertha says that Margrethe loves both men and that she can't decide between the two of them. Astrid promptly states they can always share.
Margrethe is later seen making love to Ubbe until Astrid enters the room with some warriors. she apologizes for having to arrest him. Margrethe visits Sigurd and Ubbe in their cell where the oldest brother attacks her, pushing her against the wall and holding her by the neck. He asks Margrethe why she betrayed him and she says that Lagertha told her to so but she doesn't know why but that she wanted them out of Kattegat.
Later, when Ubbe sees Margrethe again, she demands forgiveness but he says that she is a slave and he doesn't hate her. Ubbe later frees her and they marry, though Margrethe still loves both Ubbe and Hvitserk. Ubbe allows her to continue seeing Hvitserk, though she wants to make sure that Ubbe will not be jealous. He insists he will not be and the three of them retire to make love together.
Margrethe survives the Battle of Kattegat and is seen treating Torvi, who was injured. She also appears in an extended scene of "The Reckoning", speaking with Lagertha, Astrid, and Torvi.
When Margrethe is first introduced she seems to be caring and kind person comforting Ivar when he breaks down. However after she marries Ubbe, Margrethe is shown to have a very ambitious side. She keeps on urging Ubbe to kill Lagetha so that he can rule Kattegatte and that she can be Queen of Kattegatte and speaking against Lagetha saying she is weak. Over the course of 5A Margrethe starts to go increasing sadistic and crazy partly because of her ambition to become Queen and the jelously of Ubbe having an affair with Torvi, Bjorn's ex-wife. The Seer even calls her mad when she asks if she will ever be Queen. She even considered murdering Erik and Refil so that Ubbe had a better chance of ascending to be king, but in the end she did kill Erik and Refil, showing she isn't completly crazy.
|Season four appearances|
|A Good Treason||Kill the Queen||Mercy||Yol||Promised|
|What Might Have Been||The Profit and the Loss||Portage||Death All 'Round||The Last Ship|
|The Outsider||The Vision||Two Journeys||In the Uncertain Hour Before the Morning||All His Angels|
|Crossings||The Great Army||Revenge||On the Eve||The Reckoning|
|Season five appearances|
|The Departed Part 1||The Departed Part 2||Homeland||The Plan||The Prisoner|
|The Message||Full Moon||The Joke||A Simple Story||Moments of Vision|