Divine Magic is usually defined as magic which uses spiritual forces to influence the world around them. The spiritual forces have goals and agendas and react to the way in which their power is used.
Some magics like Necromancy can be used by a Divine magic user.
The Group took an oath by the Inheritors and Ember took an oath from his god. The Oath was to never speak of the Whispering Tyrant. The divine oaths bind us and prevent us with pain to speak of the events with the Necromancer.