Seto was Ardbert's companion, and during their adventures around the world Seto arouses his sentience. After the world is flooded with light, Ardbert is marked by society as a villain; Seto, angry at society for ignoring Ardbert's good deeds, settles in Wolekdorf to live with other amaros.
When the Warrior of Darkness goes to Wolekdorf in search of the crystal to break the seal of Titania, Seto refuses to hand it over and offers the Warrior a trial; once completed, he relies on the Warrior's resistance to the light. Seto then asks the Warrior to retrieve the locket of his former master who fell into the lake. Receiving the medallion, Seto bestows the crystal and says the Warrior's soul is similar to 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 make preparations before returning to the Source, the Warrior of Darkness returns 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 is nonetheless glad Ardbert can finally rest in peace. Seto senses his friend's soul within the Warrior of Darkness and the two briefly reconcile, motivating the amaro to start an adventure of his own one day.