Life is defined by have two parts, a body and a soul. The soul is host to ones Emotions, Sensations, and their ability to move and make choices, not to mention being time. The soul and body cannot exist wholly without the other. A body without a soul is quickly returned to its natural elements. A soul without a body has no tether to the world, and is forced to either wander or fade into the Suzal.
SuzalSome call it Suzal, or Aether, or The Great Spirit Mass among many other names; whatever its name, it encompasses all. It exists in tandem with the physical world, unable to directly affect or be directly affected by the physical world. It is where thoughts, dreams, feelings, and personalities dwell. It is a mirrored reflection of the world, the collective unconscious, the dreamscape, the world beyond death, life itself.
It is from the Suzal that newly generated life procures its soul most of the time. When two or more creatures unite in body and soul, a portion of the Suzal breaks away to fill the newly created void of a body. The soul of a newborn can only be obtained when their body has enough substance to hold the soul, usually half way through most pregnancies. Though much research has gone into the creation of life, many aspects of it still are shrouded in mystery, such as why it is when two or more creatures come together that a new life is formed or how the suzal generates different beings when it itself is one entity/structure/idea.
DeathDeath is defined by the separation of body and soul. This happens when the body can no longer support the soul, leading to the soul having to detach whether it wants to or not. Before one dies, they are able to prepare for a number of outcomes. Most choose to return the Suzal, to allow their soul to eternally dream. But some do not wish to, or are forced to, remain. The common being doesn't know about reincarnation or the creation of a ghost.
ReincarnationReincarnation is when a soul jumps to a new body before the fade into the Suzal. Reincarnated life has the same base personality, aura, and as their previous incarnation, but lack the memories and experience of their bodies. Any changes to the soul persists from incarnation to incarnation. Few get to choose what the reincarnate as. For the most part, higher soul masses attract the soul, so a reincarnated body would be one close those larger masses of soul (or just a massive soul itself). One could influence their reincarnation by knowing where a thick soul area is nearest to them, or knowing of a large soul that they could die near to influence what they come back as. But this is made more difficult by the fact that a creature the reincarnated would take hold of is developed enough to be amicable to a soul.
If someone is born without taking the soul of one who reincarnates, a portion of the Suzal will fill the empty shell of the body. This usually happens just as the creature is amiable to hold a soul, typically somewhere between their conception and birth. There have been reported cases of miscarriages where the newborn fails to grasp either a reincarnated soul or be filled with a soul broken away from the Suzal.
GhostsGhosts/wraiths/revenants/spirits/etc are those who attach themselves to the physical world after their body has withered away. Most that die move on to the rejoin the Suzal, or are reincarnated. For one reason or another, either by their own devices or the machinations of another, creatures are forced to stay tied to the physical world with their memories and emotions. Some stay as revenants, angry with unfinished business they are unwilling to leave behind. Some stay by accident, ghosts who have wish to move on but are unable to. Some are kept from moving on by another, forced to stay.
An object is needed to keep the soul tied to the physical world. This can be truly anything, but the most potent is the souls previous body, their corpse. They are not bound to the object in the same way they had a body in life. They can move about freely, not having to keep any portion of their soul in that object. They are also unable to affect the object they are tied to, and have limited effect on the physical world around them. A ghost is unable to detach themselves from the plane without the intervention of a life.