Gith

From Charmed

This demon has the ability to create vortexes that suck his victims into worlds fashioned according to their desires, wishes, and dreams. If told a person's desires, he can also create these pocket realms without use of the vortexes. Eventually within these realms, the indulgence of the person's desires leads to their self-destruction.

Gith feeds off the energy created by people's unfulfilled desires.