I’m going to summarize a bit.
Thief got away.
Guy by the name of Edward Carlyle shows up, claiming to know where it went. A man by the name of Travis Benton, a notable Diviner and local businessman, was responsible for the theft. Benton has formed something of a cult around himself, and Carlyle talked our heroes into going to stop him for their own various reasons.
When they broke into the Textile Mill to face Benton, they discovered he had partially built himself into a grand machine of some kind, granting him terrible powers in the form of white fire.
As they fought Benton spoke a prophecy:
“I name you Destroyers of Worlds, Slayers of Destinies! The Gods themselves shall cry their dismay at your existence and nations shall weep rivers of blood!”
The battle was quickly resolved despite Benton’s newfound powers. As they slew him, his machine exploded in a great ball of white fire, destroying factory and leaving our heroes alive, but marked with a unique, key-like version of the Mark of Destiny.