During the countless generations under the Age of Isolation, the formerly homogeneous species remembered only as "Those of Old" underwent a series of expansive adaptations. Those who lived in Heaven evolved into the Angels, and those trapped in Hell become the Demons. These changes were not fully comprehended until Reemergence, the point at which the two races came back into contact with each other.
Some romanticized the concept of the Unified, a species that over time had acquired mythic qualities as the best of both races. Thus the idea of forcefully reverting to their previous state was born. The very thought was highly blasphemous, especially to the moral court of the higher angles. And so the secret society of the Harbingers was formed of both Angels and Demons to try and find a way to achieve this seemingly impossible goal.
One of the only real theories that showed any promise was the notion of selectively breeding demons and angels together to isolate the shared genes and eliminate the mutations that had caused them to deviate. Unfortunately, the two races had become so differentiated that they were no longer capable of breeding successfully. So this course of action was all but abandoned.
The following period of stagnation was significant enough to cause much discord in the group. This, coupled with the ever mounting conflict between Heaven and Hell began to draw in more fanatic members that only saw the groups resources as a means to achieve their own goals. What was once an organized think tank of innovators became a fractured collective of followers with only a vaguely connected purpose.
The only real connecting thread between the group was the idea of creating one or a whole race of Perfect Beings. Some hoped to use this entity to achieve peace, while others proposed using it as a weapon to destroy the opposition. Others believed it could be necessary in combating a yet unseen enemy.
-Experiments- They were instrumental in implementing the process of bloodweaving in the Bloodkin, who were used as an engineered resource of both test subjects and testers.
Their efforts were more or less successful, culminating in the birth of Sloth.