It could be a new character entirely, an unknown demigod who has some special ability related to protection or construction. This character could have been sent by Chiron for some reason. Maybe they have the power to make the tent invincible or to create a sort of shield around it. And their backstory could be related to an ancient prophecy that ties them to Percy's future.
It could be an old demigod who has retired from active quests but still has a lot of knowledge and power. Maybe someone like Clarisse's older relative who has seen a lot in the demigod world and is now tasked with looking after Percy.
There could be many fanfiction ideas around the Percy Jackson series involving a 'guardian' and a 'tent'. Maybe the tent is a magical place where the guardian protects Percy from some new threats. For example, it could be a tent that exists in a realm between the mortal world and the world of the gods, and the guardian has special powers to keep it hidden.
Well, it could be about Percy having a new guardian figure in the world of Camp Half - Blood. Maybe this guardian is tasked with helping Percy set up his tent in a special area, which is full of magical protections or challenges. The plot might involve the guardian teaching Percy some new skills while they work on the tent, like a new form of combat or a way to communicate with the spirits of the forest around the tent area.
A simple plot could be that the MT tent is a secret shelter created by a powerful magician long ago. The guardian is a half - human, half - spirit who has been protecting the tent. Percy stumbles upon it during one of his adventures. The guardian initially sees Percy as a threat but then realizes he can be the one to fulfill an old prophecy related to the tent.
Artemis could be seen as the 'guardian of the hunt' in Percy Jackson fanfiction. As the goddess of the hunt in Greek mythology, she has the power and the authority to oversee everything related to the hunt. She could be the ultimate protector of the hunters and the hunting grounds.
Artemis herself could be considered the 'Guardian of the Hunters' in a way. Since she is the goddess who leads the Hunters, she has a natural role of protecting them. But in fanfiction, it could also be a character like Thalia. She has a strong connection to the Hunters and her skills and powers would make her a great guardian.
Perhaps it could be a centaur who was once a great guardian of the forest but has been broken by the encroachment of dark forces. Or it could be a minor god who was supposed to protect a certain aspect of the world but has failed and is now in a broken state. There are many possibilities within the rich lore of Percy Jackson.
In some fanfictions, Thalia's tent could hold secrets. It could be a place where ancient artifacts are stored that are relevant to the Percy Jackson world. Characters might stumble upon these secrets while seeking shelter in the tent. It could also be a place where new alliances are formed. Say, a character who was previously an enemy enters the tent and after some tense moments, decides to join forces with Percy and the gang.
There could be magical battles. Maybe some dark magic seeps into the tent, and the characters have to fight it off. For instance, a spell might be cast that turns the inside of the tent into a dangerous maze, and they have to find their way out while fighting off shadowy creatures.
Well, a big theme is loyalty. The guardians are loyal to their duty of protecting the tent, and this loyalty can be tested in different ways in fanfiction. There's also the theme of discovery. Percy or other characters might discover new powers or secrets related to the tent or the guardians. For instance, they could find out that the guardians have a special ability that has been dormant for ages. And sometimes, there's a theme of friendship. Percy might form a friendship with the guardians while they are all working together to safeguard Thalia's tent.
It could be an ancient and vengeful Titan who was once imprisoned by the Hunters' predecessors. Now free, it wants to destroy the Hunters to regain its lost power and take revenge on those who once locked it away.