This powerful illusion mimicked a noxious disease, giving the victim the look, feel, and smell of a true plague-carrier that was obviously apparent to any observer other than the victim. The caster had to touch the intended target in order to cast this spell. If the victim did not resist, they were afflicted for seven days per level of the caster. The illusion could be lifted at any time by the caster, or by a sufficiently powerful dispel magic. Cure disease had no effect whatsoever.
To others, rotting flesh smelled rotten, oozing sores felt slimy, and deformities looked real, but the victim felt perfectly normal and saw nothing amiss in a mirror. If the disease was one familiar to the caster, then the chance for someone to detect the illusion via a typical professional examination was quite small. If the disease was one fabricated by the caster or based on second-hand information, then the chance to detect the illusion quintupled.
In addition to verbal and somatic components, the caster had to touch the target and be holding a pinch of soot or fungus.
In Cormyr and Sembia, it was illegal for spellcasters to be rewarded for removing a spell that they cast themselves. Thus, in those countries, extorting money or services through use of plague was a crime.