Souls are bound to the physical forms they inhabit. They cannot be torn away against their will; they must choose to depart on their own.
The entry and exit of the soul is governed by a singular passage, a channel shared between the brain and the eyes. The essence of every soul—its unique and vital imprint—is stored as the mind. Yet the mind cannot abandon the body without the outlet of the eyes, whether those eyes are functional or ruined.
This passage is most vulnerable when the body trembles in fear or surges with excitement, though it also loosens when the body is weakened or pressed to its limit. Within each soul lies a passage engraved into its eyes, a mark that cannot be replicated. Should the eyes be destroyed, or should the vessel itself fall apart, the soul loses all ability to re-enter or depart its form.
When a body is destroyed while the soul remains unattached, the soul collapses into a great mass of memory, waiting to be absorbed, devoured, or left to wander. In time, cohesion erodes. What was once a soul dissolves into scattered remnants, until nothing remains but fragments.