Phobio/Chronology

Demon Lord Attack 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 with by Milim because he attacked Rigurd when he arrived. Phobio, humiliated by Milim, left Rimuru City after a peaceful but failed to 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 Eurazania, causing Eurazania'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.

Later Phobio regrouped with the other two of the Three Beastketeers, Albis and Suphia, and explained to the new Demon Lord Rimuru the circumstances of Milim's attack.

The Octagram Soars Brightly Arc
After Rimuru mass-teleported the joint Tempest-Eurazania forces to the battlefield in Eurazania 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-Eurazania'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-Eurazania alliance, as the previously completely unknown enemies can now be analyzed and countermeasures can be prepared in the future.

The battle ended in the Tempest-Eurazania's alliance's victory, as Clayman's forces were wiped out and the forgotten Dragon Capital forces retreated.