This mystery can be found at a place called Fornama, in the southern part of Vangrinn, directly south of Afalvat Mylna, or southwest of Hofgard Altar. As you approach the area you’ll begin to hear a dwarf named Banski complaining about being encouraged to paint all the signs to the shelters in Svartalfheim. If you want to hear the whole dialogue you should stop and wait, since when you approach the dwarf he will dive into the cave below. You’ll have to dive in after him if you want to progress the mystery.
How to Escape the Fornama Caves
When you reach the bottom of the cave system you’ll find a Jotnar note which provides a clue regarding how you can escape the area. The Jotnar trapped here have since died, but they built portals which they were attempting to use to escape, or at least evade the rats. Be sure to extract the Power of Jotunheim from one of the Jotnar before you enter the main chamber of the cave system through the small hole in the wall on the northern side.
Once you’re inside the cave you’ll find a number of Jotnar portals on the walls. Some of these lead to a Platinum Ingot, and one to an armor piece, but you don’t need to concern yourself with these to complete the mystery. Instead, you should focus on the portal at the southwestern side of the chamber. The first thing you’ll need to do is drop down to the ground near the northeastern side, drawing the rats from the southwestern side towards you. Just before they reach you, use the Power of Jotunheim on the southwestern portal to reach the barricade quickly. You can then begin to push it inwards so that you can get through.
As you reach the ledge on the other side, there will be a poisonous cloud released when you loot the Platinum Ingot in the chest. You’ll also find snakes around here, so keep your guard up. All you need to do from here is follow the path upwards on the wooden platforms, until you reach a few more barricades. You’ll need to pull these out and then climb up the wall to the surface. At this point Banski will light the oil in the area with fire, so you’ll need to be quick to avoid it. If you do get caught by the fire, have a ration ready to use to replenish your health.
When you reach the surface again you’ll see Banski in the same area where you found him initially. You can speak with him to go through a number of amusing dialogue options. Don’t worry which you choose, you’ll have the opportunity to go through all of them. The mystery will end after the conversation.