Finding Junk Town
Junktown is a very small, single room dungeon that seems to spawn in both the dungeon boss and event slots. The type of dungeon entrance you are looking for in this case, is one of the sewer manhole cover type entrances. There are some other dungeons and events that share a similar-looking entrance, but they are often minor distinctions between them, and more importantly, you will always find the Mad Merchant within an entrance that looks like this. Being able to rule out options that are definitely something else, allows you to skip over the other entrance types if you are just trying to get this one spawn in your game.
Items Sold by the Mad Merchant
The Mad Merchant doesn’t have anything particularly notable to sell. Still, if you are in need of crafting materials, he has a moderate stock of the various Irons, relative to your gear level. If you need any of these, make sure to buy them before you start hounding him about the mask.
How to get the Twisted Mask
The Twisted Mask is a special armor piece that is part of the Twisted Armor set, and assists with unlocking the Bark Skin trait, using the Wailing Tree event. As far as the armor set goes, it’s actually a 4th piece, being a second headgear item, something unique to that set. You really don’t want to use the mask as part of that armor set once you get the proper headpiece as the stats of this one are much lower.
To get the Twisted Mask, start a conversation with the Mad Merchant and ask him questions related to the mask. He will get more agitated as you do so, and upon demanding the mask from him, he will react violently and engage you in combat. The fight is a pretty easy one to win, and once you have, you will receive the mask.
Later, during the Wailing Tree event, you can interact with the tree while wearing the mask, and it will grant you the Bark Skin trait.