The main characters are a blend of the traditional Merlin - related characters like Merlin himself and the knights, and the unique addition of the Lamia. The knights could include Lancelot, known for his chivalry. The Lamia's character is often explored in depth, from her physical appearance to her inner thoughts. Her relationship with the knights and Merlin forms the core of the story, whether it's a relationship of conflict or cooperation.
The main characters are obviously Lamia and Merlin. Lamia is often depicted as a unique and mysterious character with her own set of powers and abilities. She might have a connection to the more shadowy or less - known aspects of magic.
Well, obviously Merlin is one of the main characters. He is the one with the magic and the power to save the knights. The knights themselves are also main characters, like Arthur, Lancelot, Gwaine etc. They are the ones in need of saving and are often the ones getting into dangerous situations that Merlin has to rescue them from.
In some Merlin Knights Lamia fanfiction, the Lamia might possess unique magical abilities that the knights are in need of. For example, she could have the power to heal a deadly curse that has befallen the kingdom. So the knights must form an alliance with her, which leads to an interesting story of cooperation and friendship.
The main characters are Arthur, who represents the royalty and leadership. Merlin, the wielder of magic with a big secret. And the knights such as Lancelot, who is known for his honor, and Gwaine, known for his fun - loving attitude. They all interact in the fanfiction as the knights watch Merlin, and their relationships and actions drive the story forward.
Arthur is the leader, with his sense of honor and duty. Merlin is the magical force behind the group, always using his powers secretly to protect them. The knights are like a band of brothers. For example, Gwaine is the fun - loving and somewhat reckless one, while Percival is the strong and silent type. All of them together make up the core of the story in this fanfiction.
Obviously Merlin is a very popular choice. His magic and his role as the hidden protector of Arthur make him a central and interesting character. Writers can explore his inner struggles with his magic and his loyalty to Camelot.
Another theme is friendship or an unlikely alliance. Merlin and the Lamia usually form a bond that is unexpected, and the fanfictions often revolve around how they support each other despite their differences. For example, in some stories, the Lamia may have powers that Merlin needs to defeat a common enemy. They then have to learn to trust each other.
Most likely there is a Lamia as one of the main characters. And perhaps there is a male or female counterpart who is either a human or another mythical being that she falls in love with.
I don't know specifically as I haven't read it. But it's likely that the lamia herself is one of the main characters. There could also be other characters like humans who interact with her, either as friends, foes or something in between.
Some Lamia Merlin fanfictions might focus on their backstories. Perhaps a story that delves into how Lamia came to be in the magical realm and how she first met Merlin. It could be a tale of her being an outcast in her own world and Merlin being the one to offer her a place among the good magic - users, leading to a deep bond between them.