A fast-growing, all-devouring fungoid lifeform from the planet Kastechia. In its sessile, "flowering" form it resembles orchid blossoms, and is harmless. When deprived of moisture (i.e. during the middle of the hot Kastechian daylight period), the organism forms microscopic spores which are free-ranging. Upon contact with water and CHON (carbon, hydrogen, oxygen, nitrogen) structures, each spore begins to reorganize the molecules into another sessile form. The mucus membranes of the human nose, throat, and lungs are ideal raw material for Kastechian spores.
Following initial infection, the progress of Kastechian Plague is rapid and irreversible. Within a period of 50 hours, a single Kastechian spore can totally convert an adult human body into "flowers" -- and a single human body so converted can provide enough spores to saturate a planet's ecosystem.
Kastechian spores are harmless against metal, silicates, and non-organic compounds. Spores can withstand vacuum, hard radiation, and extreme cold. Their molecular structure rapidly decomposes at temperatures above 500° C. The only known defense against Kastechian Plague is to avoid contact with spores.
It is conjectured, although not proven, that Kastechian Plague is a form of nanotech weapon created by an alien race long ago.