Spinel is a major recurring antagonist in Pokémon Horizons: The Series, serving as one of the admins of the Explorers, a mysterious organization. He is a tall, slender man with distinctive green hair and red eyes. His background prior to joining the Explorers is not detailed, but his rank indicates he holds a position of significant authority within the group.

Spinel's personality is defined by his snarky and dismissive demeanor, particularly towards his rival, Amethio. He is highly confident in his own abilities and displays a condescending, formal attitude toward associates and a seemingly unflinching level-headedness, though this composure can crack under pressure. Unlike the more direct Amethio, Spinel is a calculated schemer who prefers to operate from the shadows, relying on deception, psychological manipulation, and thorough intelligence-gathering rather than brute force. He has no reservations about using his Pokémon to directly attack humans or erase their memories to achieve his goals. His primary motivation is to fulfill the missions assigned by his superior, Gibeon, whom he obeys without question, while also being driven by a deep, almost obsessive curiosity about the mysteries surrounding Liko's pendant and the Legendary Pokémon Terapagos.

In the story, Spinel is tasked by the Explorers' leadership to investigate the Rising Volt Tacklers after Amethio’s initial failures. His role is that of a covert operative and a strategic threat. He makes his physical debut by jamming the group’s communications and later strands their airship, the Brave Olivine, near Levincia using a network of Magneton. He successfully steals Liko's pendant by luring her into an ambush and having his Beheeyem put her and her Pokémon into a trance. Although Liko and her friends eventually reclaim the pendant, Spinel manages to escape after a fierce battle where his Umbreon easily overpowers them. Later, he continues to spread false information online to mislead his targets and sets elaborate traps, such as constructing a decoy tower specifically to lure and study Friede and Captain Pikachu.

Spinel's key relationships are marked by rivalry and tension. He openly mocks and irritates his fellow admin Amethio, viewing him as flawed and unprofessional, which creates a significant antagonistic dynamic between the two. While he is formal and cooperative with other admins like Coral, Sidian, and Chalce when their goals align, he is also shown to be manipulative and ultimately treacherous. In a significant development, Spinel betrays Amethio, using a mysterious substance on his Umbreon to easily defeat him and trap him in a cave system to further his own agenda.

Spinel exhibits notable character development over the course of the series. Initially portrayed as the epitome of calm, collected, and condescending control, his facades begin to crack. When Liko, Roy, and Dot manage to defeat his Beheeyem and Magneton, he becomes uncharacteristically angry. His encounter with the giant Arboliva that emerges from the ancient Poké Ball causes him to lose his sanity momentarily, laughing maniacally at the fascinating turn of events. This shift suggests a hidden fanaticism beneath his professional exterior.

Spinel is a skilled Trainer with several notable abilities. His expertise lies not in direct combat, but in technology and subterfuge. His tactics include using multiple Magneton to create widespread electrical interference, spreading false information online to divide and confuse his targets, and wearing disguises in public to hide his identity. His known Pokémon include Magneton and Beheeyem, which he uses for surveillance, memory wiping, and setting traps. His most powerful known Pokémon is his Umbreon, a formidable battler that he uses as his ace in serious confrontations. At one point, he also utilizes a mysterious substance called Laquium to enhance his Umbreon's power. As an admin, he also holds a degree of authority within the Explorers, able to lead select groups of agents on independent missions.