I don't know for sure as I haven't read this particular fanfiction, but usually in fanfiction, Percy could be a character from a popular book, movie or TV series.
I'm not sure who Percy specifically is without reading the fanfiction. It could be an original character created by the author, or perhaps a reimagined version of a known character from a particular franchise that the fanfiction is based on.
In Percy tired fanfiction, Percy often shows signs of physical exhaustion. His usual energetic actions might be slower, like his sword - fighting skills not being as sharp. For example, in some fics, he might stumble during a fight instead of his usual confident moves.
In this fanfiction, Percy is likely a character who has been given the role of the king of monsters. Maybe he has some special powers or a unique backstory that led to this status.
It could also be Percy Weasley from the Harry Potter series. He's a Gryffindor and has his own personality quirks. Fanfic writers might focus on his intelligence, his loyalty to his family and friends, and his role in the wizarding world to make him the 'hottest guy' in their fanfictions. There are many aspects of his character that can be explored and enhanced in fanfiction to give him that 'hot' quality.
Percy could be a fan of the original work that the fanfiction is based on. Maybe he's someone who has a deep understanding of the source material and thus is in a good position to break down the fanfiction.
Well, without reading the specific fanfiction, it's hard to say exactly who Percy is. But generally, in a 'champion of the gods' scenario, Percy would be a central figure. He might be a hero with unique powers, like being able to control certain elements or having superhuman strength. He could be a character who has to face various challenges and tasks on behalf of the gods, kind of like a chosen one in a fantasy story.
In this fanfiction, Percy is a character who is the son of Erebus. But without more context from the specific fanfic, it's hard to say exactly who he is beyond this basic family relation. He could be a new take on a well - known Percy from other mythologies or stories, with different powers and a different role to play because of his parentage.
I'm not sure as the statement doesn't provide much context. Percy could be a character unique to that particular fanfiction. It might be a character created by the fanfiction author with certain special traits since they are described as 'the oldest being' in this work.