The mist exists between the fractured portions of the world. Impassible by most means, certain factions are capable of traveling from realm to realm by either teleporting or by “bridging” the area between realms in a manner reminiscent of wormhole technology. The mist itself is, in a sense, lethal; although one can come into contact with it indefinitely in certain concentrations, doing so lessens ones “reality.” Beyond a specific concentration, however, the effect becomes severe enough that the body simply cannot continue to function. It is entirely possible to use the mist for tactical purposes, as beings in mist become insubstantial and objects are capable of phasing through each other.
The Create Mist ritual should theoretically be capable of producing a single square of mist terrain, though it remains untested. (Level 5 ritual, 100 gp cost, 10 minute casting time)
The party also discovered and researched a ritual (level 6, 150 gp cost) to make an area supernaturally real and solid.