Source of arrogance

Exploration Stage: Crystals
From: Isabelle
Description: I don't want to see Marie Nouveau return to the world of the living. I am an expert in magical items. I can seal her soul completely. But first we must collect the soul stone. The huntress says she lost her ring. Find it.
Completed: It's a ring of domination. It has a big lilac diamond on it. The huntress always seemed to become arrogant when she wore it. I should have seen it sooner.