Well, growth is a significant theme. The characters in brotherhood fanfiction usually grow both individually and in their relationship as brothers. Conflict within the brotherhood can be another theme. It might be a conflict of interests or a misunderstanding that they have to overcome. And of course, there's the theme of protection. Brothers looking out for each other from various threats.
One popular theme is 'what if' scenarios. For example, what if a certain character had made a different choice during a crucial moment in the story? It allows writers to explore different storylines and character developments.
The theme of Wrath's leadership within the Brotherhood in relation to his relationship with Beth is also common. Writers might show how his role as a leader affects his time with Beth and vice versa. For example, how he has to balance protecting the Brotherhood and loving Beth. It's a complex dynamic that makes for interesting fanfiction.
One popular theme is the exploration of the characters' backstories. For example, there are many fanfics that delve deeper into Edward and Alphonse's childhood before the alchemy incident.
One common theme is loyalty. In most fanfictions, the brothers are shown to be extremely loyal to each other, no matter what. For example, they would risk their lives for each other without hesitation.
There are also brotherhood fanfics in the superhero genre. Take the Batman and Robin relationship. Some fanfics delve into their brotherly connection beyond just the crime - fighting aspect, like how they support each other through personal struggles.
One popular 'dark brotherhood novel' could be 'The Elder Scrolls: The Infernal City' which has elements related to the Dark Brotherhood. It takes readers on an adventure filled with mystery and danger.
One common theme is Rhage's struggle with his inner beast. In the original series, this is a major part of his character, and fanfiction often delves deeper into how he copes with it. Another theme is his relationships, whether it's his romantic relationships with other characters or his brotherly bonds within the Brotherhood.
The theme of revenge is quite common too. Maybe an assassin is seeking revenge for a wrong done to them or to the Brotherhood. It can drive the plot forward in a very engaging way. Also, the concept of a hidden society with its own rules and hierarchy is explored. Fanfictions might show how new recruits adjust to this strange and often cruel world of the Dark Brotherhood, with its own code of conduct that is different from the normal society's.
One common theme is their relationship development. Writers often explore how Rhage and Mary grow closer and overcome obstacles in their relationship, given Rhage's unique situation within the Brotherhood.
One common theme is the Fem OC's journey of self - discovery within the Dark Brotherhood. She often has to figure out her place in this secretive and sometimes morally ambiguous organization.