The Forgotten Ruins are just west of Purewater Run and east-south-east of Hag Rock Redoubt, between two waterfalls. She will request that you travel to the ruins and help her find her brother, Altrius, who explored them but did not return. The note invites you to investigate the promise of 'Riches Beyond Imagining', which Cassia promises can be found in Forgotten Ruins in The Reach. This will begin the quest, and Cassia's Plea will open and read itself to you.
Upon reaching level 5, the Courier will approach you, saying 'I have a letter here for you.'