It is one of the "Deletors", the bizarre beings residing on the wandering planet "Brandt" that had once approached planet Cray. It possesses the ability to turn ambient air into corrosive gases. The corroding power is so strong that even magically protected metal armours are returned to dust on contact. There is no need to say how deadly the gases are to living things. The gases, unharmful to Deletors, can act as protective barriers untouchable to hostile beings. The bodies and minds of the miserable victims are corrupted, deteriorated and eventually, annihilated.
"Deterioration" and "Fermentation", though separated by being harmful or beneficial, are of the same phenomenon in nature. This merciless deterioration is "beneficial" of course, in the eyes of Deletors.