Dropped by Hilltrolls in Mount Zhayolm. You will need to pass through either of the Gates of Halvung to access them. Passing through the gates requires checking the gate first, remaining in the zone, and then finding a Cast Metal Plate to pass through. See the map for spawn locations.
After the quest is complete, wait until the next game day and talk to Fari-Wari again. You will receive a Mercenary Camp Entry slip granting you a one time access to the Mercenary Camp BC previously only accessible to FanFest attendees. You must be at least as far as ToAU:Mission 19 to get this item.