Time

Back in the beginning of time, they trapped illness in sachets and buried them in the great walls of the city. Then many years after, during the revolution, the wall fell into pieces. The new people found the sachets, opened them, as they did not know what was in them, and the illness fell mercilessly upon everyone. One of those diseases, the worst one, went around each night from house to house and randomly blew her poisonous breath leaving a mark on every house she touched upon, and that mask could not be removed ever, by anyone. Not even to this present day.