Grim Dawn: Definitive Edition

The "Flames of Valbury" is found inside of the Port Valbury challenge dungeon in Act 3. This particular area is found on the third level of Port Valbury, which is called "Old Town." It's possible to miss it as you work your way through the dungeon. Here's the exact location of it:



When you enter this area the vines will shut behind you, then you will be swarmed by enemies. After killing everything that spawns, make sure you open the chest in the center of the room. It sort of blends in with all the Aether on the ground.

Once you open the chest the achievement will unlock. Any questions just ask :)