Reading Shadows Rising gives a possible premonition.
Turalyon wants to do what's necessary for the greater good, this includes working with his wife torturing prisoners for information - he restrained them with light chains and she was scouring their mind with void to discover secrets leaving them broken and maddened.
The novel showed how they started doing it to get info on Sylvanas from someone who knew a thing, there was a whole chapter with Turalyon attempting everything he could peacefully in vain and finally giving up and helping Alleria with that by restraining prisoner. By the time Jaina caught up Turalyon and Alleria already did this several times and seemed to be getting familiar with a method.
It is possible that while we're away - Turalyon might try consolidating power for the greater good using these void methods. So here's possible crown of light bringing darkness.