Viadu

Location
is the Mystery Merchant you will find in Val Aureum Area.
 * Chebika (on a roof south of the flight manager)
 * Barrens Outpost in Basilisk Crag
 * Lee's End Stead in Freeholds
 * Bamarama arena in Freeholds
 * Tulufan
 * Sandwalker Refuge in Aurum Road
 * Torrent Outpost
 * Cathedral Redoubt
 * Sietch Bidaum in Colossal Ruins
 * Camp Marrakeen

Mystery Merchant Shop
's shop information can be found in this list here

Trivia
The only Difference in the all of Arborea's Goblin merchants in the color of their backpack. has a what color Backpack?