There are many universes, operating on what we would call physical laws. They are made up of such things as time, space, energy, and matter; they are what we think of as reality, though between them they may be very different from on another. These are the realms of mortal beings, the froth on the crashing wave. But what the inhabitants of the Froth are ill-equipped to discern is what lies Outside.

Beyond the walls of the worlds lie realms where physical existence has no inherent meaning, and whose dreamscapes are composed of concept and essence, shaped by no laws but the wills and desires of their owners. The Outside is the home of - and largely composed of - the Extrinsics, the lords of reality and unreality.

A mortal who arrives physically in the Outside will, relatively shortly, cease to exist save by the grace or goodwill of the Extrinsic whose realm they have entered. In a very real sense, the traveller will be preserved in their host's mind and imagination, a figment, and will remain only as long as the Extrinsic does not lose interest, willfully erase them, or can be convinced to restore them to a place in conventional reality.

The only reasonably safe place for mortals in the Outside is the Realm of Remembrance, which is intended specifically to house mortals and whose host is quite sympathetic to them… but those who arrive there do so under circumstances that make their return to the Froth exceedingly unlikely.