Phobio is a proud and provocative Beastman and is sometimes quite aggressive and cheeky.
Demon Lord Attacks Arc
Phobio arrived in Tempest with the intent of taking it over, as he thought the new nation was weak. Phobio was soon angrily dealt by Milim because he attacked Rigurd when he arrived. Phobio, humiliated by Milim, left Rimuru City after a peaceful but failed talk with Rimuru.
Soon after, Tear and Footman sensed Phobio's anger, and convinced him to attain power equal to a Demon Lord to combat Milim. All he supposedly had to do was letting Charybdis possess his body and maintain control. Phobio broke the seal on Charybdis, and as Charybdis, he set out to attack Milim.
After Charybdis got ambushed by a joint Tempest-Dwargon force, and the battle reached a stalemate Rimuru realized that Charybdis had possessed Phobio. By Rimuru's request, Milim defeated Charybdis while sparing Phobio's life. After the battle, Rimuru successfully split off Phobio from Charybdis while Rimuru also absorbed Charybdis' core, effectively sealing it away indefinitely. Phobio then apologized for all the trouble he caused, and his master, the Demon Lord Carrion, in order to pay back the debt of Rimuru saving Phobio despite Phobio's previous hostile behaviour, agreed to establishing a non-aggression pact with Tempest.
Demon Lord Awakening Arc
Demon Lord Milim declared war on Yuurazania, causing Yuurazania's Capital City Laura to be evacuated. Phobio remained behind to observe the battle later and after Milim's Drago Nova disintegrated the entire Capital City in a single attack with Carrion barely surviving, Demon Lord Frey appeared and seemingly finished Carrion off, though despite Frey noticing the presence of Phobio who had been gravely wounded by the collateral, she seemed to have spared him. Afterwards Phobio managed to hang on to his life long enough to reach Tempest's outer reaches and got healed by their potions.
The Octagram Soars Brightly Arc
After Rimuru mass-teleported the joint Tempest-Yuurazania forces to the battlefield in Yuurazania to confront the joint forces of Jistav and the Forgotten Dragon Capital, Phobio also participated in the battle and teamed up with Geld in order to fight Footman and Tear, however the Footman and Tear team had a clear advantage in their battle. But Phobio and Geld were able to buy enough time for the battlefield to tilt enough into Tempest-Yuurazania's favor that Footman and Tear had to retreat, with Geld noting that the knowledge gained from the battle against the two members of the Moderate Jesters means that it was a strategic victory overall for the Tempest-Yuurazania alliance, as the previously completely unknown enemies can now be analyzed and counter measures can be prepared in the future.
The battle ended in the Tempest-Yuurazania's alliance's victory, as Clayman's forces were wiped out and the forgotten Dragon Capital forces retreated.
- Leopard Fang Flaming Palm: Essentially a powerful fire punch.
- Ultraspeed Regeneration: Phobio inherited Charybdis's regeneration power after they were fused and separated.
Phobio regards Rimuru as a "lowly slime" at first, his anger against Milim clouding his judgement and despite being shown Rimuru's aura which evidently surpassed his own, he could no longer treat Rimuru amicably. After Rimuru later split Charybdis off from him and spared him, Phobio apologized for his misconduct and started treating Rimuru with respect, even more so after Rimuru took in Yuurazania's refugees.
Initially, Phobio had tried to use force to take control of Tempest, as he saw the country of the Jura Forest a worthy area for Carrion, only to fail when he later was defeated by Milim, which causes Phobio to hate her as it left him in a situation where he had to return to Carrion empty-handed for failing diplomatic relationships. He is scared of her and what she is capable of. Phobio is only a minion of Carrion and he knows that Milim is one of the most powerful Demon Lords, surpassing even his master, therefore far surpassing his own power. Even the sight of her makes him uneasy. In his quest for revenge, he got tricked by Footman and Tear into fusing with Charybdis, causing him to blindly chase after Milim. After Milim helped Rimuru to save Phobio, he stopped holding a grudge against her. Later Carrion quit being a Demon Lord and became Milim's subordinate, causing Milim to be Phobio's new boss as well.
He respects the Beast King a lot and seems him as his idol.
- LN Volume 3: Chapter 4
- Light Novel Volume 6