Well, it could be a really interesting and terrifying addition. Maybe it could be some kind of ancient monster that was locked away long ago in the world of Percy Jackson. It could be released by some dark magic or an evil demigod. The xenomorph's ability to adapt and its deadly nature would make it a formidable foe for Percy and his friends.
Percy's water - controlling abilities would be unique in Asgard. He could use it for defense and offense. For example, he could create water shields or water whips to fight against enemies. His ability to breathe underwater might not be as useful in Asgard directly, but it could come in handy if there are any underwater areas or if he has to deal with water - based magic there.
Mermaids can fit in as another species in the Percy Jackson mythology. They are part of the rich tapestry of sea - related creatures. They might have their own relationships with the sea gods. For example, they could be servants or allies of Poseidon. Their existence adds more depth to the underwater world that Percy often has to deal with.
Percy would probably use his powers over water to his advantage. Maybe there are large lakes or rivers in the Jurassic times and he can control the water to create barriers or distractions against the dinosaurs.
Percy Jackson would probably stand out in Forks. He has this whole demigod aura and his powers are quite flashy compared to the more low - key vampires and werewolves. But he might adapt by using his wits. He could blend in by pretending to be a normal human, but his constant awareness of possible threats (which in Forks are vampires and werewolves instead of Greek monsters) would make him seem a bit paranoid to the locals.
In Percy Jackson fanfiction, Goku could be a mysterious outsider who comes to help during a great war against the Titans or some other major threat. His Saiyan fighting spirit and his various energy attacks, like the Kamehameha, could be seen as a new form of magic in that world. He might not understand all the Greek mythology stuff at first, but his pure heart and desire to do good would make him a valuable ally. For example, he could team up with Percy to fight off a horde of monsters. His super speed and strength would give them an edge in battles.
Naruto's chakra control could be seen as a form of magic in the Percy Jackson world. His ability to use jutsu like the Fireball Jutsu could be like a new type of spell. And his summoning jutsu might call upon some unique creatures that don't exist in the Percy Jackson universe.
If we consider how the Percy Jackson characters would fit into LOTR's world, we also have to think about the different races in Middle - earth. The demigods might have different relationships with the hobbits, dwarves, elves, and men. The hobbits could be both curious and a bit scared of the demigods at first. The dwarves might be interested in the demigods' weapons and their fighting abilities. The elves, with their own magic and long - lives, could compare and contrast their existence with that of the demigods. And the men of Middle - earth would likely be both cautious and eager to use the demigods' powers for their own purposes in the fight against Sauron.
She might bring in her demigod skills. For instance, her knowledge of ancient languages could help the Avengers decipher some mysterious inscriptions they find. Also, her agility and combat training from the demigod side could make her a formidable fighter in the Avengers' battles.
The balance in nature would be disrupted. Artemis is the goddess of the hunt, the moon, and nature. Her death could cause strange phenomena in the natural world, like animals going wild or the moon's cycle becoming erratic. This would not only affect the demigods but also mortals who depend on the stability of nature.
Percy Jackson would be a very interesting addition to the Game of Thrones world. His ability to control water would be a huge asset in battles. For instance, he could create floods to stop enemy armies or use water to put out dragon fire. In the political arena, he might be seen as a threat by some because of his powers, but also as a potential ally by others who want to use his abilities for their own gain.