A really interesting plot for a Regulus Black return fanfiction could be that he didn't actually die but was in a sort of stasis in the cave where the locket was. When he returns, he has a unique perspective on Voldemort's plans as he was so close to his inner circle. He could try to form an alliance with the Order of the Phoenix, using his knowledge of the Death Eaters' tactics and weaknesses. He might also struggle with being accepted back into the wizarding world after his association with the Death Eaters, which could add a lot of depth to the story.
One plot idea could be that Regulus returns as a ghost and tries to guide Harry Potter in secret. Another could be his return through some dark magic experiment gone wrong but he has new powers and knowledge. Maybe he returns to expose the true nature of certain Death Eaters who are still at large.
Well, in a fanfiction about Regulus Black's return, a great plot could involve him coming back with a mission to redeem his family's name. He might have found a way to reverse the damage the Black family has caused over the years. He could also return to help solve some of the mysteries that still linger in the wizarding world, like certain secrets in the Black family manor that could be key to defeating a new dark threat.
One idea could be exploring Regulus Black's time as a professor and his relationships with students. Maybe he has a student who reminds him of his younger self, and he tries to guide them away from the dark path he once walked. Another could be a mystery where he has to solve a magical riddle in the school that is linked to his past secrets.
Another plot could be that Regulus, reborn, has memories that are fragmented. As he tries to piece them together, he discovers new secrets about the Black family's past that could change the way the wizarding world views his family. Along the way, he forms unexpected alliances with those who were once his enemies.
One idea could be that Regulus Black, despite being a Slytherin in the original story, has a secret admiration for Gryffindor values. So, in the fanfiction, he could start secretly taking part in Gryffindor - like adventures. For example, he might help Gryffindor students in a fight against some dark forces in the Forbidden Forest.
One idea could be that Regulus, after faking his death, has been secretly working against Voldemort all this time. He could be gathering intelligence and using his knowledge of the Death Eaters to undermine their plans. Another plot could involve Regulus coming back into the wizarding world and having to deal with the changed perception of him, as everyone thought he was dead. He might also have to face his family again, especially Sirius, and deal with the complex emotions that come with it.
A third plot idea is that Harry's connection to Regulus Black affects his relationship with Sirius. Instead of being his godfather, Sirius could be more of an uncle figure. And Harry could be more involved in the Black family affairs. He might learn about the family's dark secrets and try to redeem the family name. This could involve dealing with the Black family's old enemies and allies, and Harry would have to navigate this complex web of relationships while still being the Chosen One.
One plot idea could be that the son discovers his father's past with Voldemort and tries to make amends for it in the wizarding world. He could use his unique position as the son of a former Death Eater and a hero's friend to bridge gaps between different factions. Another idea is that he has some special magical abilities inherited from both his father and the Potter side, which he has to learn to control while dealing with the expectations of others. And he might go on a quest to find hidden secrets left behind by his father related to the Horcruxes.
In a fanfiction where Regulus Black is sorted into Hufflepuff, he might face a lot of prejudice from his own family. They could be disappointed that he's not in Slytherin. But in Hufflepuff, he finds true friends who support him. He could use his intelligence (which is often associated with Slytherins) to help Hufflepuff in things like academic competitions. This would show that being in Hufflepuff doesn't mean he lacks the traits that other houses value.
One common plotline is Regulus joining the fight against Voldemort after faking his death. He uses his knowledge of the Death Eaters to help the Order of the Phoenix. Another is his relationship with Sirius. They get a chance to reconcile and work together.
One idea could be exploring the backstory of a minor character in the Star Fox universe. For example, what was the life of a mechanic on the Great Fox like before joining the team? Another could be a time - travel plot where the Star Fox team has to go back in time to prevent a major disaster that would change the future of their galaxy. Maybe they have to stop an ancient weapon from being activated.
Well, perhaps the dragon rider returns with new powers or abilities. They might use these to face an old enemy that has resurfaced in a more powerful form. Or they could return to find that their dragon has formed a new connection with another creature, causing some initial conflict before they all learn to work together.