Percy could embark on a quest to stop a powerful new evil that is immune to normal demigod powers. Since he has all the gods' powers, he is the only one who can stand against it. He might travel to different mythological realms, like the realm of the giants or the land of the fae, using his new powers to navigate and survive in these strange places.
He could go on adventures to the far reaches of the Underworld. With all the gods' powers, he might be able to access areas that were previously off - limits. He could also journey to the homes of the gods and goddesses to learn more about their powers and how to use them better.
Percy would initially be shocked and a bit scared. But then, his sense of responsibility would kick in. He would start to train himself to use the powers effectively. He might seek out the help of some of the more benevolent gods or goddesses who could give him advice. He would also have to deal with the envy or fear of others. However, Percy's loyalty and good heart would guide him to use the powers for the greater good, like protecting the demigods and the world from new threats.
Well, there could be Percy going on quests with the gods by his side. Maybe they help him face new and more powerful monsters that he couldn't handle alone. For example, fighting a giant that has been awakened by an ancient curse.
They could go on a quest to find a magical artifact that has the power to keep both the demigod world and the Twilight world in balance. Percy's skills in combat and his knowledge of mythology would be useful, while Bella's ability to understand the motives of vampires and werewolves could help them avoid certain dangers.
Maybe they embark on a journey to rescue a captured demigod. Along the way, they face various challenges like crossing a dangerous river filled with sea serpents. Percy's knowledge of the water and his brother's problem - solving skills (again, depending on how the fanfiction portrays him) would help them get through the obstacles.
Maybe Percy unknowingly breaks some ancient and very strict laws of the Gods. For example, he might interfere with some sacred rituals or places that are off - limits to mortals, even demigods like him. In the fanfiction world, the Gods could be very unforgiving when it comes to such violations and decide to kill him as a result.
Maybe he could gain the ability to transform into an Egyptian animal, like a falcon or a jackal. This would be a cool addition to his existing powers and would give him new ways to move around and fight enemies.
They could go on a quest to find a magical object that has the power to balance the magic in both their worlds. Since Percy is used to dealing with Greek mythology - related quests and Bella has her own experiences in the Twilight world, they could combine their skills. For example, Percy's ability to fight monsters and Bella's immunity to some vampire powers could come in handy.
Maybe they go on a journey to find a lost artifact that has the power to control both vampires and demigods. Along the way, they face various challenges like werewolves who don't want them to succeed and demigod enemies who see Bella as a threat. Percy would use her strategic thinking from her demigod training, and Bella would rely on her instincts from living in the vampire world.
Well, he could encounter unique mythical creatures that are specific to the woods. Maybe he'll find a hidden grove protected by dryads where he has to prove himself worthy to enter. It could also be that he discovers an ancient magic in the woods that helps him in his quests.
As Praetor, Percy could be involved in diplomatic relations within the Roman demigod community. He may have to make tough decisions about alliances and resource distribution. Also, his relationship with Annabeth might face new challenges due to the different Roman and Greek cultures. For example, there could be rules in the Roman camp that conflict with their relationship as it was in the Greek world. Fanfiction often explores how they overcome these cultural differences while Percy fulfills his duties as Praetor.