The Shar Bible
Love is a lie. Only hate endures
Reveal secrets only to fellow members of the faithful.
Never follow hope or turn to promises of success.
Quench the light of the moon and stars wherever you find them, and hide from it when you cannot prevail.
The dark is a time to act, not wait.
It is forbidden to strive to better your lot in life or to plan ahead save when directly overseen by the faithful of the Dark Deity.
Consorting with the faithful of good Patrons is a sin except in business dealings or to corrupt them from their beliefs.
Obey and never speak out against ranking clergy unless it would result in your own death.
It is told that at the dawn of time, she was the prime mover in causing the dark echo of the world to be created. (The Shadowfell)
There are references in the book that seem to strongly imply that quenching the light also seems to refer to learning and knowledge, and those that seek to spread the same.
Several Orders of priests/followers are mentioned:
The Dark Justicars: A secret order within the Priesthood, the elite and those in major favor with Shar
Order of the Dark Moon: A monastic order that focuses on the path of the shadow
Nightcloaks: Especially brutal and debased (even for the followers of Shar) group that focus more on the Mistress of the Night’s loss aspect. They kill, main and brutalize for it’s own sake.
Darkcloaks: An order that focuses on Shar’s aspects of forgetfulness. They are unusually compassionate individuals who seek to bring the solace of forgetfulness to troubled people, especially those emotionally damaged.