It could be a new monster that is after Percy. Since Percy is a demigod, there are always monsters chasing him. This new monster might be something that Paul has never seen before and it could put both of them in danger.
Another option could be a demigod from a rival group. This demigod could see Percy as a threat to their own plans or status. When Paul gets involved, the demigod might underestimate him, but Paul could end up using his wits and knowledge of the mortal world to help Percy outwit this antagonist.
It could be a new monster that is specifically targeting Percy's mortal connections, like Paul. Maybe a monster that feeds on the fear of mortals who are close to demigods.
In this fanfiction, perhaps Paul Blofis, being Sally's husband, could offer Percy some fatherly advice. He might share his own experiences and wisdom with Percy, which could help Percy in dealing with his own complex life as a demigod. Percy, on the other hand, could introduce Paul to the magical aspects of his world, like the existence of Camp Half - Blood and the different gods.
Well, Paul might be really shocked at first. Percy could show him some of his demigod powers, like controlling water. Paul, being a normal mortal, would be super amazed and probably a bit scared too.
He could interact with them in a very friendly and awestruck way at first. Like he's constantly asking questions about their powers and adventures, and the Avengers are amused by his enthusiasm. For example, he might be star - struck when he meets Iron Man and keeps asking about his latest suit upgrades.
Perhaps a rogue group of mermaids and mermen. They don't like the idea of Triton allying with Percy, a half - blood. They believe that Triton should only focus on the pure - blooded sea creatures. So they become the main antagonists, constantly attacking Percy and trying to turn Triton against him.
Another possible antagonist could be a powerful sorcerer or witch who is envious of Aphrodite's beauty and power. They see Percy as a way to get to Aphrodite. So they try to use Percy as a pawn, casting spells on him to make him do their bidding and cause harm to Aphrodite, all while Percy is trying to figure out what's going on and break free from the control.
Obviously, Percy would be one of the main characters. Then, the members of the Blofis family like Paul Blofis, Sally's new husband, and any potential siblings in the family would be main characters too. They would be important as they are the ones Percy is meeting.
In a 'Percy Meets Paul' fanfiction, Percy could be a demigod, like in the Percy Jackson series. He has powers related to the Greek gods. Paul, on the other hand, could be a normal human who is very intelligent and curious. Their meeting could be a chance encounter, like Percy accidentally stumbling into Paul's life while on a mission. Or Paul could be someone who has been unknowingly drawn into Percy's world of magic and mystery.
Well, Paul Blofis could be really curious about Annabeth. Maybe he asks her a lot of questions about her life at Camp Half - Blood. He might be amazed by her intelligence and skills.
In a 'Paul Blofis meets Poseidon' fanfiction, it's possible that Poseidon would appear to Paul in a dream first. He could give Paul some cryptic messages about Percy's future. Paul, being a mortal, would struggle to understand at first but then slowly start to piece things together. And when they finally meet in person, there could be a tense exchange as Paul tries to stand his ground in front of a powerful god.