Magma is a young man who operates as a Spider Rider, a warrior who partners with a giant spider. Unlike many other riders, Magma is not affiliated with the formal Arachna military, instead functioning as a lone wanderer driven by a deeply personal mission. His life was forever changed during his childhood when an Invectid raid destroyed his home village and killed his family, an event that left him with a lasting hatred for the Invectids. He was saved from this tragedy by a spider named Brutus, and in the aftermath, Magma took up his Manacle, the device that formalizes the bond between a rider and their partner. Through this bond, he learned of Brutus's own desperate search for his missing younger sister, a purple spider named Portia.

This quest to find Portia became the central motivation of Magma's life. He and Brutus swore a solemn promise to locate her, and this oath defines his existence as a wanderer, preventing him from settling down or joining a standing army. Magma is a passionate individual, capable of becoming obsessive about the things he cares about most. His hatred for the Invectids is fierce, but he also possesses a more excitable and even laid-back side, particularly when his other great passion comes into play: his fanatical admiration for a legendary hero named Quake. Magma has collected a large amount of Quake merchandise since he was young, and he is known to be moved to tears whenever he witnesses his hero in action.

Magma's path crosses with the main group of Spider Riders when his search for Portia leads him to the Forest of Bewilderment. There, he meets a young Earthen (a human from the surface world) named Hunter Steel. Magma initially helps Hunter, and after some time, he concludes that the best way to gain information on Portia and confront the Invectids is to fight alongside other riders. He formally joins the Spider Riders, intervening in a duel on their behalf. Within the group, Magma acts as a sort of older brother figure to Hunter, offering guidance and encouraging him to never give up. He is less trusting of new allies, such as Grasshop, a former member of the Invectid leadership, whom he frequently teases and openly insults.

His key relationships are defined by his promise. His bond with his spider partner Brutus is the most significant, built on mutual loss and a shared goal. His role in the story is largely driven by the search for Portia, which leads him to clash with major antagonists. He eventually learns that Portia and her rider, Aqune, are being controlled by Buguese, one of the Invectid generals known as the Big Four. This revelation hardens his resolve. Magma's development is a gradual journey from a vengeance-driven, obsessive loner to a collaborative warrior who understands the value of unity. He faces several defeats, losing a duel to the Invectid Stags and being swiftly overcome by Buguese in his powerful Battle Beetle, the Dark Opal. However, he perseveres, and the culmination of his character arc arrives when Buguese is finally forced to release his control, freeing Aqune and Portia for good and allowing Magma and Brutus to fulfill their long-held promise.

In combat, Magma and Brutus rely on overwhelming physical strength, capable of repelling large enemies with a single powerful strike. His personal weapon as a Spider Rider is a morningstar, a type of mace, that has the ability to switch to a flail, granting him versatile options in battle.