Modron Heart

Given by Vidyadhar, an outer plane creature you encounter during Zaviak's Vision Quest in Chapter 10, after you successfully answer his riddle ("Bees"), or by simply killing him.

In-game description
"Modrons are mechanical creatures of utter law and efficiency that make their home on Mechanus. Many think of modrons as soulless, emotionless beings without a heart to speak of, but this item proves those beliefs false. The Modron Heart is a core of pure law that strengthens its wearer in battle against chaotic creatures."