How do I get glafire???
You need perception 14 or more to find the mining room/crawler nest area. It's in the second tunnel (uphill cave) in the most bottom right place of the cave. (first one being that one where you can build a camp.) If you're under perception 14 it says that it is a dead end.
You have two spots inside the cave crawler nest area, they are both near each other in the bottom right part of the area, both being marked by a question mark.
It's the same for me... It just pushed me out after the battle.
The door leads to an other cave system filled with undead. After getting through that system you get to discover a new cave entrance, which I assume will lead to a new city somewhere in the Western part of the map. I remember reading some in-game lore about a city that uses necromancy that is in the west. (I'm not 100% sure though, so don't quote me as my memory might be a little bit fuzzy)