The First Descendant provides plenty of quests to work through but often offers little direction, including with the Magister’s Hidden Assets sub-quest, but we’ll direct you to the Core Materials you need.
The Magister’s Hidden Assets subquest in The First Descendant unlocks relatively early in your progression. But you may not immediately notice it unless you check your quests tab—and even then, there is no indication of what you need to do or where you need to go.