Lotica

Location
is the Mystery Merchant you will find in various locations around Val Tirkai.
 * Pathfinder Post hidden between two buildings
 * Field Base Lunacy Tirkai Forest, south of Pathfinder Post
 * Blightroar Research Station
 * westmost research tower, bit northwest from Blightroar Research Station (MM discord)
 * in north, near entrance to cavern that leads to Thrallhold (MM discord)
 * far south in Bridgehead, next to NPC for climbing achievement (MM discord)
 * entrance to Three Towers in Thrallhold (MM discord)
 * Field Base Tenacity in Thrallhold (reported on global chat, MM discord)
 * Camp Insanity south of Thrallhold near Skyfields (reported on global chat, MM discord)
 * Field Base Reciprocity, up on Argon tower that Invalesco are researching (MM discord)

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?