The Choir.

The Choir is the Fear of people around you gossiping, the fear of the opinions of others. It is a social Fear, and takes a very active role in the life of the victim. It is a grey, fungal, substance that infects the people it is after. 

This fungus slowly gnaws away at the flesh and the mind of the victim, slowly eroding their will to live, and as the ugly, horrid, fetid growth spreads across their body, the victims tends to wear very heavy clothing, hoping to hide both the horrible appearence of their skin and the smell rising from their corpse-like body.

The Choir spreads itself through these unwilling servants, known mockingly as greyskins.  As if the infection was not bad enough, the fungus, upon reaching the ears of the victim, will whisper and mumble words, insults, degrading the victim's self-esteem. 

It takes only a month for the infection to cover the entire body. It takes several years for it to kill. However, victims often kill themselves before a year is out.