Some ghosts, after spending enough time in the Underworld, become Geists. Geists are stranger beings, ghosts reshaped by the Underworld into powerful representations of death with a craving for influencing the living world and feel life again. This allows them to make pacts with humans who had just died or passed through near dear experiences and bring them back to life, in exchange for sharing their flesh and going to the world of the living with them. Those human-Geist hybrids are known as the Bound.