Well, perhaps the plot could involve Percy being given the tail as a sign of special favor from Poseidon. He might then have to learn how to use the tail in underwater adventures, like swimming faster or having better control in the ocean currents. It could also lead to him being able to communicate more effectively with sea creatures, since he now has a more 'aquatic' form.
His character could change in several ways. He would have a new sense of identity. No longer just a demigod with powers, but now something more 'aquatic'. He might be more curious about his father's world and want to spend more time there. This could lead to some conflict with his human side, as he has to balance his life on land and his new underwater existence. Also, he could become more of a leader among the sea creatures, as he has a unique connection to them through the tail.
Well, it could be about Percy seeking advice from Poseidon on how to deal with a new and powerful enemy. Maybe he's facing a threat that only Poseidon's wisdom can help him overcome.
In a fanfiction, Percy could discover a new aspect of his powers that is related to Poseidon's domain but in a way that no one has ever seen before. For instance, he might be able to control not just water but also the weather patterns over the ocean. When Poseidon witnesses this, he is proud of Percy's growth and evolution as a demigod. He then takes Percy on a special journey to an underwater realm that is only accessible to a select few, to further train him.
One possible plot could be Percy discovering his true parentage as the son of Amphitrite. He might struggle with his identity, as he has always known Poseidon as his father. This could lead to a journey of self - discovery where he has to learn about Amphitrite's powers and how they are now a part of him.
One possible plot could be Percy's struggle with his dual heritage. He might be conflicted between the gentle, love - associated nature of Aphrodite and the powerful, tempestuous nature of Poseidon. He could be an outcast among both the children of Aphrodite, who are often more focused on beauty and charm, and the children of Poseidon, who are known for their strength and connection to the sea. This internal struggle could form the basis of a great adventure as he tries to find his place in the world of demigods.
A great plot could revolve around Percy's role in the power dynamics among the gods. As the son of Hera and Poseidon, he has the potential to shift the balance. Some gods might try to use him as a pawn, while others see him as a threat. Percy would then have to navigate this complex political situation among the gods while also dealing with his own personal growth and the challenges that come with being a demigod.
In the fanfiction, Poseidon's visit to baby Percy could be a very solemn occasion. Poseidon, being a god, has to be careful as his relationship with Percy's mother is against the rules of the gods. He might come to bestow some of his godly essence on Percy, which would explain Percy's natural affinity for water. He could also be there to make sure Percy has a chance at a normal life for as long as possible, so he might use his powers to hide Percy's demigod scent from other monsters for a while.
Well, it could be about Percy learning all kinds of sea - related powers from Poseidon. Maybe Poseidon teaches him how to control the tides or communicate with sea creatures. For example, Percy might start off as a young boy who is a bit clumsy with his powers but as he grows up with Poseidon's guidance, he becomes really proficient.
The fanfiction might be set in a scenario where Annabeth and Percy are in a secret relationship. Giving Percy hickeys could be a risky but exciting move for Annabeth. It could then lead to a series of events where they struggle to keep their relationship under wraps while dealing with the consequences of this very visible sign of their closeness.
Well, it could be about a moment of intense passion between Percy and Annabeth. Maybe they've just had a big adventure and are celebrating privately, and in a moment of closeness, Percy gives Annabeth a hickey. It might lead to some teasing from their friends or a bit of embarrassment for Annabeth at first, but also show the deep connection between them.