As per my tradition for a double XP weekend, I had a go at a Thieve's Haven run or two to get the 5 star quests (level 16 1/2 thanks for asking)
When I finally got my 5 star emmisary quests, I only received 3 when I thought it was usually 4...no bother I'll do those 3 and then pack up for the night! After I'd completed the final one, another quest appeared with just two X marks the spots on Plunder Valley which were...a Chest of Legend and a Keg of Ancient Black powder!
How long has that been a thing? Have I been embarrassingly over looking easy XP, or is that "final quest" of the 5 star emmisary something new?