Limbo

When a person has died, but the soul does not send itself, it may instead remain in an ethereal state of Limbo as an Unsent. This is most often the fate of those who cannot come to terms with their own death-- usually due to a perceived slight, a powerful love, or some other matter of unfinished business.

In this state, the soul can observe the world of the living, but cannot interact with it in any meaningful way (except occasionally communicating through dreams). The way they see the world is largely dependent on how they perceive the world-- for instance, an Unsent who believes the world to be a dark and dismal place will literally see the world as darker and more grey than it actually is, and an Unsent who believes the world to be bright and full of hope will see their surroundings as more vibrant than they really are. Given the nature of Unsent, the former is far more likely to be experienced.

Generally speaking, an Unsent may remain in Limbo for as long as they can hold on... but the longer they remain in Limbo, the more likely they are to become a wraith. Many souls in Limbo end up either Sending themselves once they have found peace, or are sent by a ritual performed by a psychopomp.