[Name] Free League Plague [Source] Planescape [Symptoms] 
A plague created by the Lady of Pain to keep the swelling numbers of the Free League in check, which grew to an overwhelming size after a conflict called the Great Upheaval amongst the factions, where the Lady of Pain decreed that there could only be fifteen Factions in Sigil at one time. Very little is known about this disease, but any member of the Free League stood a chance of becoming infected with it simply by entering Sigil.