The characters your recruit into your guild are the backbone of your operations throughout the world. Characters age and die as normal, meaning they can and will be replaced by new adventurers as time goes by. The Iron Oath introduces a number of complex features, such as affinity, synergy, and personal goals and ambitions: Characters might not get along as you want them to, which may result in tension and even mission failure.
All characters are defined by a number of features on top of their personal views and goals. Of course, they can also succumb to various illnesses and other problems that can affect their performance. Death is particularly severe, of course.