Crevasses – basically cracks in glaciers – are a type of dungeon I first encountered in the Secret of the Silver Blades, where they lead up to the evil Dreadlord’s castle. Cringeworthy as that sounds, I’ve always loved the idea of a band of adventurers exploring the bottom of crevasses – the combination of dangerous environment, bitter cold, and even unearthly beauty is quite potent. Snowy environments are also much neglected, in my opinion, so here’s the chance to kill two yetis with one chunk of ice.
The crevasses will be a fairly irregular mess. There are similarities with caves, but the passages will mostly be narrow and long. Lots of dead ends. A similar feature – ice caves – can offer larger, covered spaces.
Use: The crevasses is probably best used as an obstacle, or rather, a passage through an obstacle – the glacier. It could connect to one or more destinations. One trope is the hidden valley full of lush vegetation, warmed by magic or volcanic vents. Another the frozen castle or similar lair. Or turn it around – the crevasses are the only means of escape from the white dragon’s lair.
The crevasses also serve as a “man vs nature” subplot. Adequate equipment, food, and protection from the cold will be essential to the protagonist’s survival.
Enemies: Since the structures are of a fairly temporary nature, your adventurers won’t find much in the way of permanent settlements. Opponents will be related to cold – yetis, snow elementals, frost giants, ice mephits, you name it. Less fortunate adventurers who fell into the crevasses could now rise as frosted-over zombies, awoken by the warmth of the player characters’ campsite.