Insanity Inducement is the power to cause madness in a person or group of people that have no mental illness. The victims lose total grip of reality becoming hostile and losing control over themselves.
The ability, or at least the Harbinger's version, of Touch of Death can evolve to become an airborne virus. Whilst airborne, those infected will begin to bleed from the eyes, nose, mouth and ears and be driven into a state of insanity and hostility.
In Red Rain, the Harbinger of Hell was able to induce insanity through an airborne demonic virus after he was vanquished, along with Hunter Caine. It is assumed that this would have led to the loss of many innocent lives. However, this was prevented when Galvin Burdette sacrificed his life to perform a ritual to remove the Ibi from those infected.