A possible plot could be that Percy and Annabeth are separated in Tartarus for a while. Percy has to find his way through a maze - like area filled with deadly traps while Annabeth is being chased by a group of vengeful spirits. Eventually, they reunite and combine their knowledge and skills to face a powerful Titan who has been ruling over a part of Tartarus and is trying to stop them from escaping.
They could discover a lost civilization in Tartarus. This civilization might have a way to manipulate the very fabric of Tartarus itself. Percy and Annabeth would then have to learn the ways of this civilization in order to use it to their advantage. Maybe they have to earn the trust of the civilization's leaders by helping them with their own internal problems first.
In some fanfictions, a possible plot development is that Percy and Annabeth discover a long - lost secret or power within Tartarus. This could be something that gives them an edge in their fight to escape or a knowledge that changes their perspective on the whole Greek mythology world. As they explore Tartarus, they may find ancient artifacts or meet forgotten gods who have been trapped there for ages. These encounters can lead to unexpected alliances and revelations that add depth to the story.
One interesting scenario could be Percy and Annabeth finding a hidden, powerful weapon in Tartarus that gives them an edge against the monsters there. Maybe it's a sword that can cut through the very fabric of Tartarus's darkness.
One idea could be Percy having to prove himself in the Underworld. Since he's the son of Tartarus, he might face unique challenges from the other denizens who fear or distrust him. Maybe he has to compete in some sort of underworldly tournament to gain respect.
A great plot could involve Percy finding a way to use the unique environment of Tartarus to his advantage. For example, there could be some sort of energy in Tartarus that he discovers he can harness to become stronger, but it has a dangerous side - like it might slowly corrupt him. He then has to struggle with the decision of whether to keep using it to get out or resist it.
The plot could involve them losing their way in Tartarus, both literally and metaphorically. They get separated from their usual support systems and have to rely solely on each other. As they journey deeper, the darkness starts to change them. For example, Annabeth might become more aggressive in her decision - making, which is a departure from her normal self. Percy struggles to keep up with this new side of her while also fighting off the demons of Tartarus.
Another plot could be that something from Tartarus has followed Percy out. A small, malevolent creature that starts causing trouble in Camp Half - Blood. Percy feels responsible for it and has to find a way to send it back to Tartarus without putting everyone in danger.
Well, a great plot could be that they find a mysterious object under their bed. It turns out to be a key to an ancient demigod treasure. So they start researching in bed, looking through old scrolls and books, trying to figure out where this treasure might be. And during this process, they also share some sweet and tender moments, reminiscing about their past adventures. Also, they could be in bed during a stormy night at Camp Half - Blood and tell each other spooky stories about the monsters they've faced, which leads to them coming up with new strategies for future battles.
One plot idea could be Percy and Annabeth starting a new life in a small town. They could face challenges like dealing with normal high school drama while still having their heroic instincts. For example, they might have to stand up to a local bully who is causing trouble for the other students. Another idea is them going on a road trip across the country, exploring different places and having adventures that are more grounded in the mortal world, like getting lost in a big city and having to find their way back using only their wits.
Well, they could face issues like how to balance their heroic duties with their married life. For instance, Percy might get called away on a quest right when they planned a romantic dinner. Or perhaps in the fanfiction, they start a school for demigod children together as a married couple, which would bring its own set of comical and heartwarming situations.
Maybe they are rivals in a quest given by the gods. Each wants to prove themselves as the better hero. Percy uses his combat skills and connection to the water, while Annabeth uses her strategic mind and knowledge of ancient places. This could lead to some intense moments where they have to decide whether to cooperate or keep competing.