Mist is a very unique artificial substance. When created ex nihilo, mist is naturally gaseous and milky white. It is composed of subatomic particles ("mistons" for lack of a better term) that are energetically more stable than normal matter. In other words, upon contact with normal matter, mist will transform that matter into more mist. However, when mist is made in such a way from normal matter, the mistons that are created will rearrange themselves to appear exactly as the matter from which they were spawned. Mist may only change matter like this if it is in its gaseous form. Hence, except under special circumstances, generation of mist is not a runaway chain reaction.
One special circumstance is when sapient matter is turned into mist. Sapient creatures made of mist may take the shape of any other object in the universe of the same mass at will. For example, if a man of mass 80 kg and a stone of mass 80 kg are both made of mist, the man may take the form of the stone and appear, to all normal analytical techniques, that he is in fact stone. He may do this at will and continues to think normally, but he will not be able to see, hear, taste, feel, or do any other such processes because he lacks the biological means necessary.
Also, anything that has been made into mist can be remade out of other mist of the same mass anywhere else in the universe at the will of a sapient creature. For example, if a two ton car is transformed into mist, then two tons of mist anywhere in the universe may take the exact form of that car if a nearby sapient creature wills it. This also comes with consequence that any sapient mist creature may disintegrate itself into mist's natural, milky, gaseous form (henceforth "gaseous mist," not to be confused with a gas made of mist) and reform anywhere else in the universe where there is the sufficient amount of mist, even if normal such travel would exceed the speed of light.
Mist was first created by a highly advanced, peaceful society on a planet in the Earth Chart. After several centuries of study and philosophical discussion, the society decided to transform its entire populace into mist. Slowly, the other sapient societies of the planet agreed to join as well, and by the time of human discovery the entire planet had been converted. The societies of this planet initially had no interest in space travel, so once the planet was converted, they simply remained there until a human exploration ship stumbled upon them.
After the SS Nascence discovered the mist world, an emissary who was particularly interested in space joined the crew.
Dark Mist is, physically speaking, identical to normal mist, except that it was created on a different planet by a different society, and the psychological disposition of the discoverer was, in reflection of its society, war-like and territorial. Thus the major philosophical disposition of all those converted to dark mist is similarly hostile, but not necessarily "evil" in such terms.
When talking about both versions of mist, dark mist is referred to as such and the first type is referred to as "white mist" or "light mist."
Non-Sapient-Controlled Properties of Mist
In its gaseous form, mist is chemically inert. Gaseous mist will transform any nearby matter into more mist, but that new mist will then rearrange itself to appear like its old form. This "material" form will act chemically just as it did before becoming mist, and it will not turn any more matter into mist.
Sapient-Controlled Properties of Mist
The really interesting properties of mist appear when a sapient creature recognizes them and wills them to appear.