The Heart of D'vouran was the name given a particular area of the living world of D'vouran. This location was originally the feeding ground for the planet and appeared as a deep pit made of living mud that ran below the surface of the planet.
The native Enzeen would lead unsuspecting tourists underground where they would lower them into the pit and feed them to the planet. Gradually, the need for the 'Heart' ended when the planet became self-sufficient. At that time, the world was able to devour people across any part of its surface by simply willing a hole that would draw them in.
The Enzeen avoided the fate they brought to tourists by wearing pendants that were actually mini-shield generators that were capable of shielding their life energy from D'vouran's hunger.
- The Complete Star Wars Encyclopedia