One factor unites the sixteen man and women featured in this book and the evil acts they committed - they all had unlimited power over the people whose lives they controlled. Their reigns of terror cover a time-span of nearly two thousand years, from the rule of Caligula over the Roman Empire starting in 37 AD to the genocide of educated Cambodians under Pol Pot during the 1980s. Motivated by power, religion, political belief, or by sadism and lust, and sometimes by insanity, they have become bywords for terror throughout the world.