One idea could be exploring the Black Sea Reaper's origin story. Maybe it was once a normal fisherman who was cursed by a sea witch. Another could be a story where the Black Sea Reaper teams up with other sea creatures to fight a greater evil that threatens the Black Sea. A third idea might be a love story between the Black Sea Reaper and a mermaid from a different part of the ocean.
Well, for Black Sea Reaper fanfiction, you could have a plot where the Black Sea Reaper discovers a hidden treasure in the deep sea. But this treasure is guarded by a powerful and ancient sea monster. The Black Sea Reaper has to use its wits and unique abilities to outsmart the monster and claim the treasure. Or perhaps a story where the Black Sea Reaper gets lost in a strange part of the ocean and has to find its way back home while facing various challenges along the way. It could also be interesting to write about the Black Sea Reaper training a young sea creature to become a protector of the sea like itself.
One idea could be exploring the Black Reaper's inner turmoil as he struggles between his human and ghoul sides more deeply. Maybe he has to make a choice between protecting a group of innocent humans or siding with a ghoul community that has shown him kindness. Another could be a time - travel plot where the Black Reaper goes back to a crucial moment in his past to change something, but discovers that changing the past has unforeseen and dangerous consequences. And a third idea could be a story where the Black Reaper teams up with an unlikely ally, like a human detective who is also trying to solve a mystery related to the ghoul underworld.
One idea could be a story where a new character, with the power of a Grim Reaper, arrives at Beacon Academy. This character has the ability to see the souls of the Grimm and can communicate with them in a strange way. They could be initially seen as a threat but end up helping Team RWBY in a big battle against a horde of powerful Grimm.
A really interesting plot would be if Ruby's Reaper form was somehow connected to an ancient prophecy in the RWBY world. Maybe it was foretold that a Reaper - like figure would either save or doom Remnant. This would put Ruby in a very difficult position, with different factions having different views on her and her new form. Also, a plot where Ruby has to team up with some unlikely allies while in her Reaper form to take on a common threat could be cool. These allies could be former villains who see the greater danger that requires Ruby's power.
One possible plot idea could be a crossover where Naruto characters gain powers from the DxD universe and have to face a new, powerful enemy. For example, Naruto could learn about the Devil Pieces system and use it to strengthen his allies in Konoha. Another idea might be a story where a character from DxD ends up in the Naruto world and has to adapt to its ninja culture while also using their own unique abilities to help or hinder the existing power balance.
A possible plot for an Overwatch Reaper OC fanfiction could be that the OC is a new recruit in an anti - Overwatch group. Reaper is sent to deal with this threat, but discovers that the OC has a connection to his past that he had forgotten. This connection makes Reaper hesitate in his mission. Meanwhile, the OC has to decide whether to use this new - found knowledge to their advantage or try to reach out to the tortured soul that Reaper has become.
Well, you could write a sea patrol fanfiction where the crew has to deal with an environmental disaster at sea. Maybe there's a massive oil spill and they have to work with other agencies to clean it up while also trying to find out who's responsible. Or perhaps a story where the sea patrol gets caught in the middle of a territorial dispute between two countries and has to navigate the political and dangerous waters to keep the peace.
A possible plot could involve a time - traveling aspect in the 'human first contact reaper fanfiction'. A future human, who has seen the destruction caused by the Reapers, travels back in time to the moment of first contact. This person tries to use their knowledge of the Reapers' weaknesses to stop them from ever establishing a foothold on Earth, but they have to deal with the disbelief of the people in that time period.
One idea could be a story focused on a small, rag - tag group of survivors who have to band together to take on a Reaper - controlled outpost. They might not be soldiers, but ordinary people forced into extraordinary circumstances.
One idea could be Percy discovers an ancient underwater civilization that was lost and forgotten. It has its own unique culture and magic. Another could be Percy having to team up with a sea monster he once fought to save the ocean from a new, greater threat. Maybe he has to go on a quest to find a powerful sea - related artifact that can restore balance to the seas.
One plot idea could be that Battle Angel is sent on a mission to stop Reaper's latest terrorist act in the Overwatch universe. Along the way, she discovers that Reaper has a hidden motive related to his past in Overwatch. This could lead to a series of battles and tense encounters as she tries to figure out his true intentions.