Complete the operation The Secrets of Andraste and have an Inquisition level of 4 or more for this to appear.
The Alamarri runes found in the mountain passages outside Haven have finally given up more of their secrets, pointing to one of the larger islands off the northern coast of Ferelden. The island is quite large and covered in dense wilderness, so searching it will be an involved process. According to the runes, however, there should be some connection to the original disciples of Andraste and the “Guardian” of the Sacred Ashes.
I know of a few adventurers trustworthy enough to send to the islands. Let them search and report back to us.
Leliana - 4:00:00
This requires stealth: A few skilled agents given enough time to quietly search the islands.
Cullen - 3:12:00
As soon as we show interest in the area, others will follow. So, let's go in force and occupy the islands.
We found what we were looking for: an ancient vault all but buried in the thick vegetation at the heart of the island, no doubt untouched for over a thousand years. The effort to open the vault without setting off traps was considerable, and what we found within was… interesting. According to an agent named Rion, this was the retreat of one of the last of Andraste’s disciples, a guardian who fled some manner of attack on the site of the Sacred Ashes. He expected reinforcements by other disciples who never arrived. Whatever texts the man thought to preserve have mostly crumbled, but we recovered a number of other artifacts from the site. It is a significant find that will undoubtedly prove of great interest to Chantry scholars, even if it will take them years to sort through all the debris.