GoArch:Unexplored Branches
From Guild of Archivists
Unexplored Branches is the name of the expanded universe for the Myst and Uru franchises. The Branches are an umbrella for works associated with, authorized by Cyan, or otherwise considered to have high canonicity, but not within the boundaries of full canon.
Unwritten is officially designated as a part of the Unexplored Branches. The exact boundaries, nature, and future of the concept has not been revealed by Cyan.
Intangible assets - a group of undeveloped ages and places that Cyan started working on.