A dream self is another feature of the wonderful world of the Incipisphere; an alter ego that's supposed to awaken whenever the real person falls asleep. Dream selves are not independent entities, but simply representations of the dreamers.
Dream selves operate from lavish towers on the moons of Prospit and Derse, in dream duplicates of their real bedrooms. Whether one's dream self exists on Prospit or Derse appears to be determined by or associated with particular personality traits, perhaps placing each player in the Kingdom that they are most suited to, or manifesting players on the appropriate moon in accordance with their self-image and projection of themselves. In the context of the extended zodiac, the personal quality that reflects moon-assignation is referred to as Lunar Sway and can be applied to people regardless of whether or not they have a dream self (including in the real world), as it is determined by personality. Lunar Sway is a key factor in determining one's extended zodiac true sign.
Dream selves are projections of what the players want themselves to be.
Dream selves also have the ability to fly. Dream selves are usually asleep when the real self is awake, and awakening a dream self causes the real self to fall asleep immediately.
The method of awakening one's dream self is to face (often unpleasant or traumatic) things one has not before.
It's possible that the dream self of one player in every session (potentially always the Hero of Space) starts out awake.