A major theme is the relationship with the god Hephaestus. In many fanfictions, the OC son of Hephaestus tries to understand their father, who is often distant. Also, craftsmanship and the creation of magical items are common. These OCs are usually good at forging, and they might create something that helps in a big adventure or in solving a camp - wide problem. There's also the theme of loyalty, to the camp, to friends, and to their own values.
One common theme is self - discovery. Since the OC is a son of Hephaestus, they often have to figure out their unique powers and how to use them. Another theme is acceptance, both within the Hephaestus cabin and among the other demigods at Camp Half - Blood.
The theme of family also stands out. His relationship with Hephaestus and how it affects his relationships with other demigods, his mother, and the rest of the camp. In some fanfictions, Hephaestus might be a more present and guiding figure in Percy's life, while in others, their relationship might be more strained, but it always has an impact on Percy's family - like connections within the demigod world.
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.
Common themes include acceptance. The OC has to find a way to be accepted by the other demigods who may be wary of him because of his father. Redemption is another theme sometimes. Maybe the OC has made mistakes or has been associated with 'evil' because of Hades, and they strive to prove themselves. And the theme of fate also pops up often. They wonder if their destiny is set because of being the son of Hades or if they can change it.
One great 'Percy Jackson OC son of Hephaestus fanfiction' is 'The Forged Hero'. It follows the story of an OC named Leo Jr., the son of Hephaestus. He has to face challenges in the Camp Half - Blood and prove himself worthy. Another interesting one is 'Hephaestus' Hidden Son'. It shows the OC's journey in discovering his powers and his place among the demigods.
One frequent theme is the exploration of the unknown. The oc, being new to the world of the gods, gets to discover all kinds of things with Hephaestus. There's also the theme of acceptance. Hephaestus, who might be seen as an outcast among the gods, and the oc, who may not fit in in their own world, find acceptance in each other. It's a really heartwarming aspect that many writers like to explore in these fanfictions.
One common trope is the outcast status. Since Hera is not the most liked among the gods in the Percy Jackson universe, her son is often made an outcast among the demigods. Another is the special powers. He might have some unique abilities related to Hera's domain, like control over family bonds or something similar.
One common theme is identity. Since Percy is the son of Erebus, he has to figure out who he really is now. Another theme is acceptance. He has to deal with how others in the Percy Jackson world accept or reject him because of his new heritage. And of course, there's the theme of power. With his new connection to Erebus, he often has new and sometimes dangerous powers that he has to learn to control.
There are several common themes. First, there's the theme of adaptation. Percy has to adapt to the new rules and expectations that come with being the son of Osiris. Second, family is a big theme. He has a whole new family connection in the Egyptian pantheon, and how that affects his relationship with his Greek family (like Poseidon) is often explored. Third, there's the theme of discovery. He's constantly discovering new things about himself, his powers, and the Egyptian mythology in these fanfictions.
One common theme is identity. Percy has to figure out who he is now that he's the son of Helios, different from his previous understanding of himself as Poseidon's son.
One common theme is power struggle. Since Percy has two very different sources of power as a demigod and as the Son of Sparda, he often has to figure out how to control and use them. Another theme is identity. He has to reconcile his two identities and figure out who he really is.