What every breathing, living being has. In their “baby” form, when they are not sure of what form to take on just yet, they are a simple, calm, white flame. It has a consciousness, and if it wants to, it can take any shape or form. For example, if a soul wants to be a man, it'll take the form of a man; if it wants to be a dog, it can take the form of a dog; if it wants to be a plant, it can take the form of a plant. There's NO limits to what the soul can transform itself into JUST AS LONG as they are in the Spirit Realm. Flesh Realmers are forced to have their souls entrapped in flesh, so when a spiritual being leaves the Spirit Realm, whatever form they are in will be surrounded in flesh.