Book 4 in the Iron Gods campaign: A great threat is rising in Silver Mount, but a precious item belonging to a mysterious entity called Casandalee has yet to be found. With the Dominion of the Black still an ever-present danger, players must navigate a dangerous canyon, the Scar of the Spider, in hopes of learning more about their enemies, and to accomplish their mission.

Alkenstar, City of Smog, is a bastion of civilization in the magic-warped region known as the Mana Wastes. Its ingenious citizens survive in the treacherous Spellscar Desert with the help of canny inventions like guns and clockwork automatons, but now their construct protectors have begun to run amok within the city. It falls to the PCs to venture beyond the city walls to find the source of their strange behavior.