Hailing from Meltokio in Tethe'alla, Zelos Wilder was born into nobility as the son of the reigning Chosen and Mylene Wilder. The Oracle of Cruxis forced his mother into marriage against her heart, while his father maintained a separate affair. This neglect defined Zelos’s childhood, leaving him primarily raised by the family butler, Sebastian. Scarce maternal attention and paternal absence bred profound feelings of inadequacy, prompting him to shield himself with a veneer of charm and confidence. A childhood trauma unfolded when his father’s half-elf mistress attempted to assassinate him to secure the Chosen status for her daughter, Zelos’s half-sister Seles Wilder. Amidst a snowy ambush, Mylene sacrificed herself to protect Zelos, condemning his existence with her final breath. This event cemented Zelos’s aversion to snow and deepened his self-loathing, compounded by his belief that Seles would have been a worthier Chosen. Seles received lifelong imprisonment for her mother’s crime, fracturing their once-close bond. Though the tragedy instilled prejudice against half-elves, Zelos later opposed anti-half-elf legislation and accepted half-elf companions like Genis and Raine Sage. As Tethe’alla’s Chosen, Zelos wielded political influence second only to the king. Meltokio’s aristocracy showered him with superficial admiration, which he manipulated to cultivate a womanizing reputation. He leveraged charm and status to graduate top of his class at Sybak’s Imperial Research Academy despite academic struggles in non-mathematical subjects. Disillusionment with his role led him to accept Pronyma of Cruxis’s offer: spying in exchange for relinquishing Chosen duties. Zelos first encountered Lloyd Irving’s group in Meltokio, using his influence to aid negotiations over Colette Brunel’s condition. His limited assistance branded him a traitor when the group defied the Pope. Throughout their journey, he displayed ambiguous loyalty—luring the party into a Fooji Mountains trap that allowed Renegades to seize their Rheairds. Suspicious disappearances and veiled betrayal hints foreshadowed his double-agent role. In Flanoir, a pivotal narrative branch determined Zelos’s fate through Lloyd Irving’s choices. Should Lloyd reject companionship during "An Evening in Flanoir," Zelos betrayed the party at the Tower of Salvation, revealing covert work for Cruxis and Renegades. This betrayal masked his true intent: he later rescued captured allies and exposed his triple-agent status, having manipulated all factions to support Lloyd’s group. His actions dismantled the Pope’s authority and exonerated the party. Zelos exhibited protective instincts, notably saving Sheena Fujibayashi from a closing Otherworldly Gate and consistently advocating for her. He aided the party in navigating political obstacles, such as persuading Princess Hilda to grant access to Heimdall. Combat prowess stemmed from his Cruxis Crystal, granting enhanced physical abilities, flight via golden wings, light-based attacks like Shining Bind, and moderate elemental magic. He wielded swords or daggers with fluid, acrobatic flair, emphasizing misdirection and agility. Keen observational skills detected subtleties like allies’ physical changes or imposters through scent. Later events reaffirmed Zelos’s loyalty and perceptiveness. Two years after the world’s regeneration, he shielded Emil Castagnier and Marta Lualdi from Richter in Palmacosta. He openly challenged disparaging remarks about Lloyd and rejoined the group to rescue his captive sister Seles. His sharp senses identified a Lloyd imposter by artificial scent, proving pivotal in resolving the conflict involving Richter and the attempted opening of the monster world gate.