How to mass murder

In history it was a common way to capture people for either getting them compliant to your ideas or killing them. Let’s sum up the ways and means for depopulating lands:

1. Some kind of (imaginary) delict
2. Fear
3. Torture

The job itself is done by some mad man, instigating the people. An impressive demonstration that this works was done at the medieval age as the inquisition was on its way. Regarding the fire burning, is it still correct calling it ‘the Dark Ages’ ..?