Zegion

Zegion (ゼギオン) was originally an injured insect that Rimuru found in the Great Jura Forest, tasked with guarding the Treants' settlement upon being taken in. He was later appointed as the Guardian Overseer of the Ten Dungeon Marvels, and also received the title of "Lord" as one of Rimuru's Twelve Guardian Lords. Zegion is also one of Rimuru's Three Top most powerful subordinates, standing alongside Benimaru and Diablo.

Original
During his debut, Zegion appeared to be an extremely large beetle with characteristics of both stag beetles and rhinoceros beetles.

Humanoid
Later he evolved into a humanoid form that looks like a warrior clad in pitch-black exoskeleton with visible golden joints. A red-tipped, sword-like horn protrudes from his forehead. The exoskeleton took the form of Rimuru's preference. After undergoing Rimuru’s Harvest Festival ritual the Magisteel given to him by Rimuru that had previously evolved into Adamantite has evolved into Hihiirokane.

Personality
Zegion typically maintains a calm and serious demeanor, speaking sparingly and choosing his words carefully. However, his loyalty to Rimuru burns with an intense fire, and any perceived insult directed towards Rimuru swiftly ignites his anger. Zegion possesses a soft spot for Apito, viewing her as a cherished sister, and he consistently prioritizes her well-being. Having been saved by Rimuru in the past, Zegion reveres him as a godlike figure who plans meticulously and exudes humility. Grateful for Rimuru's kindness, Zegion is determined to prove his own worth, constantly seeking to enhance his strength, even though he is already formidable.

Background
Zegion was born directly from Zelanus in the Otherworld alongside Apito who was birthed by Peliod to fill in the remaining vacant spots in the Twelve Insect Generals. However, Zess, wary of their potential, eventually attacked them, forcing the pair to flee to the Central World.

When they arrived, the pair were immediately attacked by a Blade Tiger. Zegion fought and defeated the blade tiger but was heavily injured. Fortunately, they were found by Rimuru who was impressed by the small insect's display of strength. Sensing Rimuru coming to him and Apito, he attacked Rimuru recklessly, to serve as bait and allow Apito to flee, only to be stopped by Apito herself when she asked for Rimuru's protection due to her recognizing Rimuru's strength and his intention to help them. Rimuru agreed in exchange for Apito providing him some honey. Due to their injuries, Rimuru patched them up with his own slime body to aid the healing process and replaced their missing exoskeleton parts with processed magisteel. He was named and tasked to guard the treants' settlement.

Trivia

 * In a recurring gag, Zegion and Apito meet Milim Nava, who scares them to the point of motivating them to become stronger.
 * Zegion, a disciple of Veldora Tempest, has been trained in the Veldora-Style Killing Arts.