Lucien was the founder of the Lothanasi Order, also known as the Lightbringers. While he did not invent the idea of worshiping the gods of the Lightbringer Pantheon, he did revolutionize the way that this worship was practiced on the continent of Galendor.
For 4200 years after the Great Darkness, the Aedra and Daedra Lords fought a back-and-forth battle in the human lands of Galendor, all of them working independently to gather worshipers to themselves, with no one gaining a lasting advantage over the others. Priests and shamans were commonplace and held the ears of the kings, but most of them were corrupt and indebted to one or more daedra. Finally, in -800 CR, Kammoloth appeared to Lucien, a young priest of Kammoloth who lived in the kingdom of Metamor, and called him to start a new order that would purify the priesthood and bring people back to the way of light.
In his many years of wandering that followed, Lucien gathered an alliance of eight other pure-hearted beings who shared his vision; together they formed the heart of the new Lothanasi Order. Lucien and his High Council organized a group of priests with a standardized code of conduct and a commitment to deal with all of the gods on a neutral basis; this would allow them to act as arbiters in disputes between the followers of the various gods, and to act as ambassadors to all of the gods on behalf of mortal-kind. In effect, the Lothanasi pledged to serve the interests of mortals first and foremost, and to do so by negotiating deals with whatever god was most needed to fill a given need. In keeping with Kammoloth's charter, however, the Lothanasi refused to recognize the nine daedra lords as legitimate deities, viewing them as the enemies of mortals and the "true" gods of heaven.
The Lothanasi were persecuted at first, but in time they came to dominate religion in human, Elven and dragonish lands alike. The daedra were once again on the outs among the civilized races, labeled as "aberrant" deities whom it was forbidden to worship. Lucien himself founded a bloodline of priests that still exists to this day, though as of 707 CR it has only one known representative: Raven hin'Elric, the high priestess of Metamor.