 Invisibility is a side-effect of this, as the wearer is temporarily pulled into the spirit-world.Immortal beings, however, became trapped in their bodies over long periods of time, subject to reincarnation only if their bodies were destroyed.Tolkien used the first part of "The Silmarillion", the creation account, to describe his thoughts on the origin of evil in his fictional world, which he took pains to comport with his own beliefs on the subject, as accounted in Tolkien's "Letters."