The core rulebook mentions Goblin Markets briefly. I was always very intrigued but also very confused how they worked. This PDF only supplement fills in the blanks of not only how to create your own Goblin Market, it also gives explicit instructions on how to run a stall. It also has some example markets that can be dropped down into any running story. This is a must have for anyone intending on creating a story that spends any significant amount of time in a Goblin Market.