Another interesting plot could be that an enemy uses a powerful spell to make Medusa forget her love for Black Bolt. Black Bolt then has to find a way to break the spell. Along the way, he might have to face challenges alone that he would usually face with Medusa by his side. This would show his growth as a character and his determination to get her back.
A post - apocalyptic Inhumans setting where Medusa and Black Bolt have to fight to protect the remaining Inhumans. They could face new threats and challenges that test their relationship and leadership skills in a whole new way.
Love and loyalty are very common. Their relationship is a central part of Inhuman lore, so fanfictions often explore how deeply they care for each other. For example, stories might show how Medusa stands by Black Bolt even in the toughest of situations.
Perhaps the son could find himself in a situation where he has to prove himself worthy of his royal heritage. This could involve facing off against enemies who underestimate him because of his youth. He then uses his unique combination of his parents' powers to overcome challenges and earn respect. The story could also explore his relationships with other Inhumans in the process.
One common theme is their relationship. Given their status as husband and wife in the Inhumans' lore, many fanfictions explore the depth and complexity of their relationship. It could be about how they support each other in difficult times.
I've heard of 'Black Bolt's Silence and Medusa's Voice' which is a unique take. It plays on the fact that Black Bolt can't speak and Medusa is often his voice in a way. The fanfiction really digs into the psychological aspect of their relationship and how they communicate on a deeper level.
One idea could be a time - travel plot where Percy goes back in time and meets a younger, different Medusa before she was turned into a monster. Another could be a story where Medusa somehow gets a chance at redemption and Percy has to decide whether to trust her or not. Maybe a plot where they have to team up to defeat a greater evil that threatens both of them.
One interesting Black Bolt fanfiction could be about his early days in the Inhumans society. It might explore his struggle to control his powerful voice and how he overcame that. Another could be a story where he teams up with other superheroes from different universes to fight a common enemy. And there could also be a fanfiction focusing on his relationship with Medusa and how they deal with the challenges within the Inhumans' leadership.
Maybe Bolt travels back to a time when the Akatsuki was at its peak. He could use his knowledge of future events and his own skills to try and take on the Akatsuki, creating a whole new set of battles and alliances. For example, he might form an alliance with Itachi before his death and together they could try to take down the other Akatsuki members.
One plot idea could be that Bolt and Penny Lemon go on a wild adventure through a magical forest filled with talking animals. Another could be a mystery where they have to solve the disappearance of an important item in their town. Maybe they also time - travel and experience different eras together.
One idea could be Percy has to face Medusa again, but this time she has an army of stone minions. Another could be that Medusa was actually cursed by a more powerful god and Percy has to find a way to break it. Maybe Percy discovers Medusa has a long - lost relative who is being held hostage and he has to make a deal with her.