I have'nt had much success with it myself,hmmm, will try it again later. I did notice a) Against powerful armies, especially Marignon, it did squat. b) don't cast it in a province your attacking because it will target YOU not the ai
By the time i reach that point in research i've got Well of Misery going and am using Harvester of Sorrows (Metallica
) and Legion of Wights with a dash of Plague and Black Death for flavor
.