Shadows of Acheron
Dark Dawn is a secret society with notably nefarious intent. Their symbol is a black sun rising.
Dark Dawn is in direct opposition of The Faithmarked.
The party uncovered Altruis Whisperwind as a member of this society, and he was using his post as one of the Judges of Argent to set up a massive network of underground tunnels beneath the capital city, and was using them to smuggle illegal magical weaponry into the city for a hostile takeover.