Souls

A soul is the spiritual life essence of a person or animal, which resides within a physical body while the person or animal is still alive. After their physical body dies, or is destroyed, their soul continues to exist, and typically moves on to an afterlife. However, some reincarnate. All animal souls supposedly reincarnate upon death.

History
It is unknown how souls came to be. Interestingly, all humans and animals alike possess souls, but deities do not as deities cannot be killed or destroyed the way humans and animals can, all deities are immortal. Before deities and angels began collecting human souls, every human soul, upon death, would simply reincarnate, their soul going into the next human baby born. Some deities saw that the human soul had worth, that it contained power and complexity unlike anything else in the entire multiverse, thus some deities, like God and His angels, or the Greek God Hades, began collecting souls. However, if a soul has unresolved business to do with their mortal life, they will be sucked into the pocket dimension known as Limbo where the soul will be transformed into a ghost.

Characteristics
A soul, whether it is a human or animal soul, cannot be destroyed, only transformed (for example, devils have the ability to twist a human soul into a demon). A soul also does not fully leave the physical body until 24 hours after death (Earth Time). If the soul is ready to move on after 24 hours, it will be transported to an afterlife dimension or be reincarnated. If the soul is not ready, it will go on to the Other Side and become a ghost.