Got to play a little bit more today. Had enough energy to go with a group and take on a whole tier 1 run, and did it without dying. Ended up having enough crowns afterwards to buy and learn a bunch of recipes, and craft my first level 2 item!
So the level progression... It's randomized from a few rooms depending on what depth you're at, and what's in each room depends on how many minerals of each type you decide to donate when the time comes. As a result, nobody ends up having the same experience twice.
Case in point, instead of going into the woods for depths 5-7, the group I was with went through an abandoned city, with a glorious treasure vault at the end. It was beautiful. : D
Well, one step closer to unlocking tier 2. Just gotta keep at it...