From publisher blurb: Times are tough for adventurers in Aden, and the high-paying bounties offered by the Cogswheel Irregulars in Mekanus are a great place to save up a few crests for traveling. As representatives of the Urbanan government, however, the player characters soon find themselves in the crosshairs of a group eager to retrieve forgotten secrets from the most dangerous parts of the city, and they are only the first ones to paint a target on the characters' backs! Heart of the Machine includes the following: An adventure in four acts! A primer and map of Mekanus, the largest city in the Known Lands! Details on the mercenary lawmen known as the Cogswheel Irregulars! New NPC profiles and bestiary entries!