Seto originally belonged to a counterfeit jeweler in Amh Araeng who abused and mistreated him. Ardbert, after hunting down the man with his party for a bounty, recognized Seto's intelligence and decided to make the amaro his companion. During their adventures around the world, Seto's sentience was aroused. After the world was flooded with light, society marked Ardbert as a villain; Seto, angry at everyone for ignoring Ardbert's good deeds, settled in Wolekdorf to live with other amaros.
When the Warrior of Darkness ventured to Wolekdorf in search of the crystal to break the seal of Titania, Seto refused to hand it over and offered the Warrior a trial; once completed, he relied on the Warrior's resistance to the light. Seto asked the Warrior to retrieve the locket of his former master who fell into the lake. Receiving the medallion, Seto bestowed the crystal and said the Warrior's soul resembled that of his former master.
I see... His journey continues. Then I will not yet bid him rest. With you, he may look forward to many more adventures. It has been a while since last I flew. Perhaps I too will go on a little adventure. Ride the winds, seek the horizon... Yes. I think perhaps I will.Seto to the Warrior of Darkness
After the battle against Elidibus and as the Scions made preparations before returning to the Source, the Warrior of Darkness went back to Seto, entrusting Ardbert's powerless Crystal of Light to the amaro. Saddened that the Ascian used his partner's body for evil deeds, he was nonetheless glad Ardbert could finally rest in peace. Seto sensed his friend's soul within the Warrior of Darkness and the two briefly reconciled, motivating the amaro to start an adventure of his own one day.
Seto is an intelligent, speech-capable amaro. He is a kind and gentle soul and very fond of people. His protectiveness over people initially made him hesitant to trust the Warrior of Darkness with the final relic to unseal Titania, a dangerous Lightwarden without a display of strength. Seto cares for Ardbert deeply, and is bitter towards the people of the First for labelling the First's Warriors of Light as villains. He is finally able to lay his grievances to rest when the Warrior of Darkness clears Ardbert's name and slay the Ascian using his body.