The Gnistorm is a group of trillions of microscopic Gni that form a cloud that flies through a city, infecting everyone if engulfs. The Gnistorm is only seen after a stage-2 infestation has been declared.
The Gnistorm was first used in the Darkside War in 7.2 billion BM when the Gni had need of a quick way of infecting huge numbers of hosts in a short amount of time. They found this method after infecting a big pile of bodies and tearing all of them into small pieces which caused all of the remaining pieces to fall apart on moleculair level. The result was a dust of trillions of small Gni like creatures that are obedient to Emperor Gni.