No one really knows what the Dreamlands are. It'd be hard to say that the Dreamlands actually exist; they don't have any physical form, and nothing that happens within the Dreamlands has any kind of effect on the physical world. Any harm inflicted in the Dreamlands is purely transitory; it does not affect the dreamer's physical body or any other actual thing.
Ordinarily, people who dream simply dream. What they dream is a concoction out of their own imaginations. Their consciousness may, at least in theory, reside in the Dreamlands while they're dreaming. But normally, the people, places, events and so on that they dream are entirely fictionalized.
Some people are, through talent or study, lucid dreamers. They are able to decide to dream, purposefully and with control over their dreams. Some of these people are able to range out beyond their own dreams (known as a "domain"), and touch the dreams of others.
Due to certain metaphysical events, the barriers between dream domains have broken down, which has enabled ordinary people to lucidly dream, albeit with less control than true lucid dreamers. Moreover, the power of Chaos has seeped into the Dreamlands, causing ordinary nightmares and, for lucid dreams, visions of things with flaws. What is seen depends upon the dreamer. If they are dreaming of the Pattern, for instance, the one they see might have a great crack down the center. If they are dreaming of a person, they may be missing an eye, or have slurred speech, or something else unfortunate.
Here's how these abilities work for normal people (i.e., people without specific dream-gifts):
- Anyone may still dream normally — i.e., have an entirely ordinary, mundane dream.
- Anyone may have a basic lucid dream, in which they can freely shape the environments within their own dreams (i.e., their own dream-domain).
- Every dreamer always controls his own mind and body within a dream; he has full agency, regardless of whose domain he is in.
- Anyone may have a basic lucid dream, in which they attempt to find the dream of another person. To do this, they venture out into the Dreamlands, which they can shape in a manner similar to a Pattern-walk shaping shadow. With a coincident dreaming-time, and absent any active prevention, they can generally find another person in the Dreamlands.
- When an ordinary person finds someone else in the Dreamlands, they are entering someone else's dream, which that other person can shape. They may be able to do some shaping within that other person's domain, but the other person has the dominant control. +compare can be used to compare relative strength of will in this regard, but any consequence should reflect that the dream-domain's owner is really the one whose mind primarily shapes the dream, and therefore the other person has limited ability to affect it against their will.
- Entering someone else's dream does not offer any capability to spy on their dream, read minds, or otherwise invade the other dreamer's domain. The other person can prevent their intrusion entirely, if they so wish.
- In a lucid dream, any participant may wake up at will.
Dream gifts modify these behaviors in ways that are specified in the gift text.