Since being altered at the Tower of Magi in 776 IE, the strain of mushrooms has suffered several different blights over the years, none of them being too devastating or long lasting. Avernums mages always managed to either cure the blight or altered the mushrooms to resist whatever disease was affecting them at the time.
The blight, that occurred in 877 IE, was irreversible. It appeared for the first time in the Northern Frontier and slowly spread throughout the entire net of caverns. The wizards' and gardeners' efforts were futile, as the blight would prove to be immune to their experiments. The mushrooms that the Avernites had come to rely upon for nourishment would not grow any longer as they did in the past.