Welgaia, the Holy City, is a city on Derris-Kharlan. It is populated entirely by angels, and is the main base of Cruxis. The only way to enter the city is through the Tower of Salvation. It is filled with high technology and computers that serve as archives.
Welgaia is visited twice by Lloyd Irving and his companions. They first enter the city to find a "Mana Fragment" to cure Colette Brunel's Chronic Angelus Crystallus Inofficium. On their way, they are captured by Kratos Aurion and thrown into jail. Regal Bryant is able to break them out using a technique with his hands, and they escape into the city, pretending to be Colette's prisoners. They receive a fragment of mana after claiming they are couriers for Kratos, and after learning about the nature of Derris-Kharlan and Mithos Yggdrasill's "New Age" project, they escape through the Tower of Salvation back to Tethe'alla. The group returns to Welgaia on their way to prevent Mithos from forcing Derris-Kharlan from its orbit around the worlds of Sylvarant and Tethe'alla, which would leave both worlds to die due to the loss of mana generated from Derris-Kharlan itself.
After one of Lloyd's companions is possessed by Mithos and taken to Derris-Kharlan, the group follows them before being caught in a trap, finding themselves separated throughout Welgaia. Lloyd finds his possessed companion and releases them from the spell. Together, they find their other companions, who are imprisoned in pairs and scattered throughout the city. Mithos, in spirit form, uses the weaknesses of each character's heart and mind to create inner struggle, but their trust in Lloyd allows them to resist Mithos's psychological games. When everyone is reunited, they find the "Derris Emblem", which is the key that allows them to enter Vinheim.