Dark World

An entire, self-contained, world/universe from a work (or multiple works) of fiction with consistent canonical history and logic. Dark Worlds often contain things like established lore, magic systems, and unique physics.

Works of non-fiction (or stories based on true events) do not occur in a Dark World and instead occur in a derivative of the real world (sometimes called a "Light World")

Synonyms: Cannon, Fictional world, Cinematic Universe

The Marvel Cinematic Universe (MCU) is a Dark World
I want to establish a Dork World for the new book I'm writing
Did you know that "Rick and Morty" and "Gravity Falls" share the same Dark World?