I knew an executive several years ago who was a skilled dispenser of poison. She would tell you in confidence about what someone had said or done. You might, if you were lucky, eventually discover that her account was completely false but at the time, since it was said in confidence, you would not be inclined to check up on her remarks. She never alleged anything extreme that might require prompt corrective action but the comments were just negative enough that they might, down the road, prevent an assignment or quietly sidetrack a career. In short, she dispensed slow-acting poison.
Her practice was discovered when a few people compared notes on what they'd suspected. By then, she was close to leaving the organization and nothing was done. Those who knew the truth, no doubt, wondered what had been said about them and how it might have affected their reputation. There was no reason to believe that anyone was immune.
Normal, honest, people find it difficult to imagine such conduct. Most of us operate with the assumption that people are usually truthful. We scoff at conspiracy theories and suspected plots. It is hard for us to imagine the mindset of someone who would so casually and needlessly harm others.
All of which reminds me of a historian's explanation of what caused Neville Chamberlain to believe that the Nazis would comply with the Munich agreement:
Neville Chamberlain had never met anyone like Adolf Hitler.