He knows everything
Our tale begins in the Shrieking Shack where Peeves often comes to meet his boyfriend Peter. Today, Peter seems upset.
Peeves asked, "Petey, what's wrong?"
Peter muttered, "When You Know Who spoke to me last, he said that he knew all about you. He said that if I ever question his orders or went against him, he would track you down and find a way to erase you from existence."
Peeves frowned. "That's impossible though, I'm already dead."
Peter told him, "I thought so too, but he just told me he would find a way like he always does."
Peeves reassured him, "There's no need to worry about any of that anyway because as long as I stay here, I'm fine. As long as you keep following his every order, then you're perfectly fine too."
Peter sighed. "I guess."
Peeves responded, "I promise you that I will be on my guard from now on."