Spirits

See Also: Ghosts
 Spirits are inside every sentient being capable of qualia (consciousness) on the island. They are what are sometimes called souls. They are what the gods of creation consume for food. 
Spirits can be removed from a body by choice, like in the instance of Spirit Walking or Dream Travel, or by force by Spirit Transference. 
They are also removed from the body in death and are consumed during the transformation into vampirism. 
In the case of the death of their body, spirits that stay on Earth instead of seeking a god to consume them become ghosts. 
Spirits cannot survive long on this world without a body. The body is their anchor to our world and they will drift off into the cosmos without constrained effort to remain. This effort takes up a lot of their energy and without recharging, the spirit can dissolve if they refuse to let go.
For a spirit to recharge without a body, they must drain the energy from another spirit. To drain the energy of another spirit, the spirit will suck it out through the mouth of the body. If the entire spirit is consumed, the body will be dead.
A spirit cannot enter or occupy a dead body. A spirit can enter a living body. However, if that body is not occupied by its spirit, when the original spirit comes back, it usually throws out the imposter automatically. For extremely strong spirits, they might be able to fight the original spirit off entirely, or partially, and remain in the body instead of, or alongside the original spirit. 
It is somewhat rare for a spirit to be able to enter a body already occupied by its soul. The only way this is possible is for those with the ability to Communicate with the Dead. Only they can open themselves up so that their spirit will not automatically fight to remove the intruder and the two spirits can communicate. A body with multiple spirits will secret ectoplasm from its pores. 
Without a body, spirits are naturally invisible to the human eye, but the stronger they are, the more that changes. If a spirit has recently fed on another spirit, it will appear as a smoke like semi-transparent figure. It will look like the person's soul would have looked, and not their physical body. Ugly bodies can have beautiful spirits and vice versa. 
Spirits are very attuned to music and some musicians have the ability to harness spirits with their songs. The music gives the spirits enough energy to temporarily form into wispy figures, but the figures are under the sway of the music almost as though they are hypnotised and the musician can use the music the control them.