Paul might be a bit intimidated at first. He's just a mortal, and Poseidon is a powerful god. But he might also be curious. After all, he loves Percy, and Poseidon is Percy's father. So he could start asking questions about Percy's heritage and what it means for Percy's future.
Paul Blofis would likely be a mix of fear and fascination. On one hand, Poseidon is an all - powerful deity, and his presence alone could be overwhelming. But on the other hand, Paul has been involved with Percy and his world for a while. So he would also be eager to learn more from Poseidon, about Percy, about the world of gods and monsters. He might start off being very polite and respectful, trying not to offend the god in any way.
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.
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.
It could be friendly. Paul might be friendly and welcoming towards Annabeth, seeing her as an important person in Percy's life. He could offer her a place to stay if she needs it in the mortal world.
They might be terrified. Poseidon is a god and his power is overwhelming. They could start trembling or even faint at the sight of him.
Paul might be characterized as the voice of reason. In a world full of chaos and mythical beings, he can be the one who tries to find logical solutions. He could be a bit of an amateur detective in the fanfiction, using his teaching skills to research and figure out things related to the demigod world. Also, his relationship with Sally gives him a deeper connection to Percy and a motivation to be involved in the demigod's life, so his protective side towards Percy can be emphasized.
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.
At first, Percy would likely be angry. He has faced so many challenges with the belief that his father was on his side. The betrayal would make him feel like all his efforts were in vain. He could lash out, perhaps even using his powers in a more reckless way. But as time goes on, he might start to question if there's a deeper reason behind Poseidon's actions and try to find out the truth, especially if he still has friends who believe in him and encourage him to look deeper.
The other sea deities would likely be excited and perhaps a bit envious. Some might offer gifts and blessings for the unborn child. The mermaids and mermen could start preparing grand celebrations in anticipation of the new addition to the underwater royalty.
There could also be a situation where Poseidon's family eventually comes around. Maybe his more open - minded relatives see the love between Poseidon and Sally and decide to support them. They could offer their protection and help during the pregnancy. Sally's family, with time, might also learn to accept the situation and be excited about the prospect of having a half - god grandchild or relative.
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.