This is a neat and quite unusual low-level adventure, suitable for existing characters or for a less-usual 'funnel' (as per the Dungeon Crawl Classics RPG rules) for starting characters who are primitive barbarians in a world brought low by some cataclysm... or indeed a more conventional fantasy world where the characters come from a barbaric tribe on the far fringes beyond civilisation.
The backstory explains what is really going on, then the adventure starts with the discovery of two dark holes belching green smoke in a recently melted end of a glacier. If you have chosen the 'Barbarian' option, the characters come from the local tribe and are dispatched by the tribal elders to investigate, otherwise the characters are approached in a frontier town by some barbarians asking for their aid, saying that the place is forbidden to them hence the need for outsiders to investigate what is going on.
The adventure then proceeds apace with a lot of unusual features to negotiate - a true test of the character's mettle in both figuring things out and being capable of engaging in combat when necessary. Each location is well-resourced with descriptions and with a range of outcomes depending on what the characters decide to do, with ample provision to aid the GM in troubleshooting potential adventure-stopping accidents. Detailed referee maps are provided, and there is an appendix giving appropriate barbarian occupations for those groups who take the barbarian route into the adventure.
Nicely thought out and unusual adventure.