Envelopes of Transposition

...ve discovered a thin leather pouch in the desk of the gorfrosċ that seems to be the leader here. We determined it is quite likely linked to another in the possession of those further up the Cabal  command chain. Some of the others have already bandied about using them to deploy a magical payload of sigils, runes, and glyphs.
Grim as it is, I know a good plan when I hear one. We may have to revisit it later.
~ passage from the journal of Svali during her adventures with the Champions of Hardhaven.

A tool employed by an unknown number of the gorfrosċ working with the Cabal, only one has been discovered and recovered - it remains in the possession of the Champions of Hardhaven.

Utility

In order to activate the envelopes, one must simply insert a piece of parchment, letter, or even small book or pamphlet. Once done, close the flap and hook it shut. The inserted item will disappear - always with another appearing in its place. If an incompatible item is inserted and the pouch is shut, nothing will occur.

Access & Availability

To the knowledge of the Champions, they have the only pouch within a considerable distance. As far as they are aware, there may be many within the Cabal, being used as instant long distance communication - or there may be two in the world, one in their possession.

Discovery

The Champions found the envelope when they raided a research outpost within the bore worm tunnels off of the Ðyrs Flow. When they had already dispatched the scientists within the foul laboratory, they noticed a slight blip of magic and found the strange leather pouch. Within they found a letter, seemingly freshly arrived, informing the overseer of the laboratory that his outpost was to be shuttered.
Since its discovery, the envelope has been tested once, and a blank paper was sent through the envelope, disappearing to parts unknown.