You question the Convictors to find out what they know about the heretics.
This quest is available if you have completed the quest Sounding Out the Amphitheatre.
Starting the Quest
Talk to Alphinaud in Coerthas Western Highlands to begin the quest.
Question the Convictors
Go to the quest icons on the map to find a Boorish Banneret, a Boorish Bowman, and Luciae. Talk to them in any order.
Speak with Pierriquet
Go to the quest icon in the map and talk to Pierriquet to complete the quest. There will be a cutscene.
Aether Current Quest
With the completion of this quest, you can now start the blue quest "Protecting What's Important" in the Coerthas Western Highlands. Completing that quest will attune you to an Aether Current in that area.
Next Main Scenario Quest
After you complete the quest, talk to Estinien to accept the next quest: Purple Flame, Purple Flame.