For the At Peace trophy in Voice of Cards: The Forsaken Maiden, you must find a fallen masked youth on the North Isle. After completing The Tale of the Ivory Maiden, return to the North Isle after some time passes. (We had explored the East Isle then returned.) Make your way to the northwestern side of the North Isle to find the Masked Soldier near the Mystic Forest.
Interacting with the card will trigger a cutscene and the trophy will pop shortly after!