Harry Potter himself is, of course, the central character. Snape is also very common as he is Harry's teacher in occlumency in the original books. Hermione and Ron often make appearances as well, as Harry's best friends. They might be involved in helping Harry learn or just be there for moral support.
Friendship is also a theme. His friends may play different roles in his learning process. Some might support him unconditionally, while others might not understand what he's going through, which can create interesting relationship dynamics within the fanfiction.
In this type of fanfiction, the relationship between Harry and Snape can be re - imagined. Snape was Harry's teacher for Occlumency in the books, but often their interactions were tense. Fanfic writers may change this dynamic. They could have Snape be more patient or Harry be more receptive, which would lead to a different kind of mentorship and a new understanding between them.
Snape is often a central character as he was the one teaching Occlumency in the original series. Harry Potter also frequently appears since he was the one receiving the lessons. Hermione might be included as well, as she is always eager to learn new magic and could be interested in Occlumency.
Some fanfictions might focus on Harry learning occlumency in a more collaborative way with his friends. For example, Hermione could be helping him study the theory behind it while Ron provides moral support. This can add a new dynamic to the story. Also, there could be a plot point where Harry discovers some hidden secrets about occlumency that are not mentioned in the original books, which then leads him on a new adventure to understand it better.
Hermione is often a common character. She might help Harry research and understand the ancient magic, using her vast knowledge from the library. Ron could also be there, providing his loyalty and sometimes comic relief during Harry's journey of learning ancient magic.
Snape is a character that could play a major role. Given his past with dark magic, he might be a reluctant mentor to Harry, guiding him in understanding the power and danger of it. Dumbledore, too, would likely be in the story, as he is always concerned about Harry's well - being and actions.
Characters with natural Occlumency in these fanfictions are usually depicted as having an edge in the magical world. They can be portrayed as being able to keep their thoughts and emotions hidden effortlessly, which makes them excellent spies or secret - keepers. In some fanfics, they are also shown as having a deeper understanding of the human mind and magic's connection to it because of their natural ability. This allows them to manipulate situations in ways that others can't. For instance, they might be able to sense when someone is trying to use Legilimency on them from a greater distance compared to those who have to learn Occlumency.
Severus Snape is also a popular choice. His complex character and vast knowledge of magic can create interesting dynamics when he meets characters from different magical worlds. He could either be a mentor or an antagonist in these crossovers.
Obviously, Harry is a main character. Hermione might also be there as she is good at potions and can help Harry. And Snape could be a prominent figure as he is the potions teacher.
Obviously, Harry is one of the main characters since it's about him learning parselmagic.