I believe that these entities somehow exist outside the normal boundaries of space/time and are usually perceived according to the state of mind of the percipient. In other words, if your head is filled with snakes, you're going to perceive these entities as demonic. If you're a "fluffy bunny" type, you'll perceive them as angels or space brothers. It's kind of like an acid trip in that regard.
This notion of self-replication calls to mind the controversial question of Genetic Memory: "Can an individual's memories be somehow contained in cellular tissue, and passed down to progeny, so that memories, dreams or even abilities are shared with the inheritor of the original tissue?"