Paired Pages

Expensive and rare pieces of parchment – when something is written on one, it spontaneously appears on the other. Often used by rulers and politician to communicate across their kingdoms at great distances. Often used as Palimpsests, but still degrade over time. Come from The Learned Canyons, and are expensive and difficult to find. 
Not every change is reflected between paired pages; if the parchment is burned or waterlogged, for example, the other copy will remain unchanged. only writing and drawing, as well as a group of vaguely understood practices known as "unscribing", are transferred over. unscribing includes everything from scraping ink from the page to wiping a chalk-slate clean, from using special chemical washes to using magic to erase writing on pages - is very highly valued. Some people are employed as specialised Unscribes to work with Paired Pages.
They were only used in the canyons, as well as parts of The Giteri and The Srem, until around 900 years ago when their popularity greatly increased and spread, as the Learned canyons had grown to a critical size with the increased use of paper in Dow around the time of the Scrivener Culture.
Sespedel is a paired-page unscribe in Rhythonze.

Utility

• long-range, instantaneous, secure communication between two locations.

Manufacturing

Occasionally a book that is being actively written, or that the location of is known, is found in the library (often by listening for the sound of scribbling). If the other end can be located, a Paired page set is now usable. There are special scriptoria where loud and rhythmic writing is carried out en masse, to help "manufacture" paired pages.

Access & Availability

Only discoverable in The Learned Canyons, valued by rulers, spies and wealthy merchants. extremely valuable, especially the further one gets from the Canyons.