Grover Underwood has been Percy's best friend since his portrayal in the films. He's a satyr and the designated Searcher at Yancy Academy to watch over Percy. He also guides the demigof to Camp Half-Blood and accompanies him on quests, with the goal of finding the lost god of the wild, Pan.
Other than being part of Percy's inner circle, Grover also has duties in the amp Half-Blood and is tasked with locating demigods.
While the specifics of Grover's early life remain shrouded in mystery, it is established that he is the son of unnamed Satyrs and the nephew of Ferdinand Underwood. The narrative in “The Lightning Thief” suggests that Grover had prior interactions with his uncle before Ferdinand's unfortunate transformation into stone by Medusa.
Grover's journey intersects with that of three young demigods – Annabeth Chase, Luke Castellan, and Thalia Grace. Attempting to guide them safely to Camp Half-Blood, the group faces adversity from Hades' forces due to Thalia being a child of Zeus. Thalia ultimately sacrifices herself, turning into a protective barrier for the camp. Grover carries a lingering sense of guilt for his perceived failure to prevent her fate.
Meeting Percy
Five years later, Grover is assigned to Yancy Academy and befriends Percy, realizing Percy is a demigod. Grover, along with the centaur Chiron, protects Percy from monsters. Unaware to Percy, Grover is his guardian.
Grover shields Percy from the knowledge of the Greek mythology world until Percy's encounter with a Fury. The narrative unfolds with Grover, Percy, and Sally Jackson facing a Minotaur. Post-incident, Grover continues his protective role, accompanying Percy on a quest to retrieve Zeus' master bolt.
In his quest to find Pan, Grover falls captive to Polyphemus. Teaming up with Percy, Annabeth, Tyson, and Clarisse, they successfully overcome Polyphemus and employ the Golden Fleece to heal Thalia's tree.
Now, the satyr was able to continue his duty in the next installments with new characters. Grover discovers two demigod siblings, Bianca and Nico di Angelo. Together with Percy, Annabeth, and Thalia, they went on a quest to rescue Artemis. In The Battle of the Labyrinth, Grover successfully locates the god.
Following this, he returns to the camp, battling monsters and conveying Pan's passing to the council. Despite being branded a traitor, Grover resolves to spread the news of Pan's death and contribute to the creation of a new wild.
In The Last Olympian, Grover, initially put into a slumber, participates in the Battle of Manhattan. Afterward, he becomes a council member and receives the title “Lord of the Wild.” While in The Blood of Olympus, Grover leads the satyrs, assuring the nymphs that Gaea is no longer stirring.
Grover and Percy's journey
Surprisingly, there's more to Grover than just being a protector of demigods. He ages slowly, which is why he appears to be a satyr pretending to be a 12-year-old in the new Percy Jackson series. Despite his guardian role, Grover has a specific list of things that scare him, like being underground, encountering Cyclopes, feeling leporiphobia (fear of rabbits), and dealing with his worries about Dionysus, Juniper's anger, and ghosts.