The plot could involve Percy having to prove himself worthy of being the grandson of Hephaestus. Maybe there are some tasks or challenges set by the Hephaestus cabin. He has to use his wits and newfound skills related to Hephaestus' domain like metal - working and machinery understanding to overcome these. And all this while still dealing with the regular threats that come his way as a demigod.
In this fanfiction, perhaps Percy's connection to Hephaestus causes some jealousy among other demigods. He might be shunned or targeted by some who think he's getting special treatment. Meanwhile, he discovers a hidden power within himself that is related to Hephaestus' abilities, like the power to manipulate fire in a unique way that no other demigod can. This new power becomes crucial in a major battle against an ancient evil.
Well, one possible plot could be that Percy discovers his new relation to Hephaestus later in his adventures. He might then start to have an affinity for creating and fixing magical items, which could be a new skill for him in battles against monsters. He could also meet other descendants of Hephaestus who teach him more about his heritage.
A possible main antagonist could be a rogue Hephaestus - related creature. Maybe a mechanical monster that Hephaestus created long ago but it went out of control. It could be targeting Percy specifically because of his new - found relation to Hephaestus, seeing him as a threat to its own existence or purpose.
Well, the plot could be centered around Percy's attempts to bridge the gap between his father Poseidon and his grandfather Zeus. There have always been tensions between the two gods. Percy, using his unique position, tries to bring peace. But there are forces at work, like some rogue demigods who don't want peace between the two powerful gods. They try to sabotage Percy's efforts, leading to a series of adventures and challenges for Percy.
One possible plot could be Percy discovering his relation to Dumbledore. Maybe he starts having strange dreams or visions that lead him to the wizarding world. He then has to learn about his new family connection while also trying to keep his demigod identity a secret from most of the wizards, as they might not understand it.
One possible plot could be Percy using his Uchiha heritage to gain new powers. For example, he might unlock the Sharingan which could enhance his battle perception in the demigod world. He could then use this newfound ability against his enemies, like the Titans or monsters. This would create a whole new dynamic in the Percy Jackson universe as he combines his demigod skills with Uchiha powers.
One possible plot could be that Percy Jackson's grandson discovers a portal that leads to the wizarding world. He soon learns about Voldemort's reign of terror and decides to use his demigod powers to stop him. Along the way, he teams up with some young wizards and witches who are also against Voldemort.
Percy could be accidentally caught in the middle of their relationship drama. For example, Aphrodite might use Percy as a way to make Hephaestus jealous. Or Hephaestus could mistake Percy's innocent interactions with Aphrodite as something more, and Percy has to prove his innocence while also trying not to get too involved in their godly relationship issues.
In the fanfiction, perhaps Voldemort's grandson is not as evil as his grandfather. He could be trying to redeem his family's name. Percy Jackson might initially be suspicious of him but then they team up. The grandson could teach Percy some basic magic, and Percy could teach him how to be brave in the face of real danger, not just the kind wizards face. They might go on an adventure together to retrieve a powerful artifact that could change the fate of both their worlds. This would be a great way to explore the idea of good and evil not being so black and white.
One common theme is Hephaestus' role in helping Percy with his quests. Since Hephaestus is the god of blacksmiths and craftsmen, he might provide Percy with a special weapon or tool. Another theme is the exploration of Hephaestus' relationship with his children in the context of Percy's interactions with them. For example, how Percy might help a Hephaestus - descended character come to terms with their heritage.
One idea could be that in the fanfiction, Hephaestus discovers Aphrodite has a special interest in Percy Jackson. Hephaestus, being the god of the forge, could create some sort of magical item that ties Percy to their story. Maybe it's a charm that makes Percy visible to the gods' love affairs in a way he wasn't before, and he has to navigate the complex relationship between Hephaestus and Aphrodite while also dealing with his own demigod duties.
One plot idea could be that Percy Jackson gets caught in the middle of a feud between Aphrodite and Hephaestus. Maybe Hephaestus asks Percy to retrieve something that Aphrodite has stolen from him, which leads Percy on a wild adventure filled with Aphrodite's love - related traps and Hephaestus' mechanical defenses. Another idea is that Aphrodite decides to use Percy as a pawn in her game to make Hephaestus jealous, creating all sorts of romantic chaos for Percy. Or perhaps Percy discovers a secret pact between Aphrodite and Hephaestus that has far - reaching consequences for the demigod world, and he has to figure out how to deal with it.