The other way is to infiltrate the Temple. One way is to slaughter everything in your path to reach your goals. You have two fundamentally different ways of approaching the quest. Galesingers are Chanters and can be looted for Scale Armors and Exceptional Crossbows. Mindgazers are Ciphers and leave behind Scale Armors and Fine War Bows when killed. Faithbinders are Priests who can be looted for Fine Breastplates and Fine Morningstars. Swordsworns are Paladins who can be looted for Plate Armor, Exceptional Swords and Exceptional Medium Shields.
Crescentsworn are Fighters who can be looted for Plate Armor, Exceptional Swords and Exceptional Large Shields. They leave behind Monk's Outfits when killed. Tidalfists are Monks that will frequently target spellcasters with their Flagellant's Path ability.
Ondra's faithful will be throughout the area. The quest triggers once you have completed The Iron Flail quest.