Yes, there are quite a few. Some explore alternative power dynamics between Morgana and Merlin within the fanfiction realm. You can find them on various fanfiction websites like Archive of Our Own.
Well, power and control are major themes. Morgana's control over Merlin as a slave sets up a situation where power is constantly being negotiated. Also, themes of redemption can be present. Maybe Morgana realizes the wrongness of her actions and tries to make amends. And there's often a theme of secrecy too. Merlin might have to keep his true self and his magic a secret while being a slave, which adds to the tension.
One common theme is redemption. Morgana, in the role of a slave, often has a chance at redemption through her relationship with Merlin. Another theme is power struggle. Since Morgana has been in a position of power before, her new status as a slave creates an interesting power dynamic with Merlin.
One popular 'morgana as slave merlin fanfiction' is 'The Unlikely Bond'. In this story, Morgana's situation as a slave leads to a complex relationship with Merlin. Another good one could be 'Morgana's Redemption'. It shows how Morgana's character develops in this unique role and her interactions with Merlin.
One great 'Merlin Morgana fanfiction' is 'The Bond Beyond Magic'. It delves deep into their complex relationship, exploring how their powers could have been used together in a more united way against the common threats in Camelot. It presents a unique take on their dynamic, showing that they could have been allies instead of adversaries.
One great Merlin and Morgana fanfiction is 'The Enchanted Bond'. It delves into their complex relationship in a way that stays true to the characters' personalities from the show. The author does an excellent job of creating a believable world within the fanfiction.
One possibility is that there would be a great deal of tension. Old Merlin has seen so much and has his own wisdom, while Morgana has her own powers and motives. Maybe Merlin would try to persuade Morgana to abandon her dark path. He could use his experience and the bond they once had to appeal to her better nature.
Their relationship could develop in a complex way. If Morgana ties up Merlin out of anger or suspicion initially, but then realizes she was wrong, it could lead to her feeling guilty. This might make her more open to Merlin's friendship in the future, and they could gradually build trust.
She might be shocked at first. Given that in the original story Morgana has her own complex relationship with magic, seeing Merlin's magic could stir a mix of emotions in her, like envy or a sense of relief that she's not alone in her magical abilities.
In fanfiction, Evil Merlin can be depicted as a mastermind behind many dark plots, while Morgana is the face of the chaos they create. For instance, Merlin might be the one secretly pulling the strings, using his magic to make things happen, and Morgana is the one out in the open, using her charm and power to intimidate others. They are like two sides of the same evil coin, complementing each other in their wrongdoings.