Elden Ring: Where to find the Golden Order Principia

One of the prayerbooks found in the Lands Between is the Golden Order Principia. You can learn two more incantations in this prayerbook: Radagon's Rings of Light and Law of Regression. The Law of Regression allows you to heal all afflictions afflicting you, while Radagon's Rings of Light create enormous rings of light that can do a lot of damage. The Golden Order Principia can be found in Elden Ring here.

To receive this prayerbook, you must first travel to Altus Plateau's capital city. The Draconic Tree Sentinel boss must be defeated and at least two Great Runes must be obtained. Great Runes can be obtained from Rykard, Godrick, and Radahn to gain access to the capital city. You'll need to make your way down to the main road and across to the dragon's wing once you've arrived in the city. To get to Godfrey's boss area, climb the dragon's wing and then the tree roots.

Once you've defeated Godfrey, you'll be allowed to search the boss chamber. To get to the higher level of the boss arena, go outside to the balcony and climb on the tree roots. Exit the building, hang a left, and leap to the roof.

To get to the other side of the upper floor, go through the broken window. Follow the balcony around to the opposite side, where there is a tree root. Grab the prayerbook from the chair suspended from the ceiling by hopping on the tree root. To retrieve the prayerbook, you don't have to hop on the chair; standing on the tree roots will suffice.