In Thraben, Tamiyo helps Jace regain clarity through a story, then challenges his assumption that understanding Avacyn will be simple. He wants to save people; she has come to record and understand the catastrophe. They agree to a limited attempt in which her mind anchors his while he examines the angel.
The encounter becomes a fight. Jace briefly stills Avacyn and learns that her influence carries the madness outward, but that something else is affecting her. He also perceives that she remains a barrier against another threat. Removing the immediate danger could therefore dismantle a protection they do not fully understand.
Avacyn recovers and tortures Jace. He asks Tamiyo to open a powerful sealed scroll, but she refuses to break her promise or unleash that story as an emergency weapon. They have gained crucial knowledge without gaining control of the situation. The dilemma is real: surviving this room and safeguarding the plane are no longer obviously the same action.