Hey, what kind of magical hazards and exploration stuff can I throw into the Crustal Caverns?
Just brainstorming:
Icy walls in a cave. They need to smash through one or more to get to a new passage. If they smash the walls they may take damage from icy shards that fly about. Fire might melt it without harm.
Icy chute that they have to keep their balance on, and when they get to the end, they are scattered onto a frozen underground pond. They slide across the pond and if they don't dig into the ice with some object (a weapon, a piton, etc.) they will smash against a wall or slide into a pit.
A (15') chasm that they need to cross, but there is no bridge. They may try to jump, but that's risky. One of the PCs sees a pile of ladders off to one side. When they investigate, they realize that the ladders are just a reflection on the ice. They need to trace the light/reflection through an icy maze. They can map, navigate, spot, or help another, to follow the reflections to the actual pile of ladders. Each round they stay in the ice maze, it gets colder and colder (after the first round...they start to take damage). The DC to get to the pile might be DC 10 and they need to make x successful ability checks based on what they decide to do for the group. The way back out is more difficult DC 15. (If the party decided to mark their trail or leave something on the ground as they journeyed forth, you can make it easier).
Just some quick ideas. Hope they help inspire you. (Hope you get them in time).