Disclaimer: I don't own RWBY. That includes its characters, the idea, the story, etc.
"This is the beginning of the end, Ozpin. And I can't wait to watch you burn."
The woman in front of him smirked as she said this, her red eyes glowing. Ozpin calmly sat still, legs crossed, despite being a prisoner. There were no chains to bind him, no cage he was locked in. No, he was free to roam if he pleased. But there was nowhere for him to go, and he had no power here.
The woman knew this as well, and took her time tormenting him, mocking mankind's struggles. He rebutted, and she retorted, both in a calm fashion as though they were discussing the weather. Any casual observer would never know that they were both mortal enemies.
"You won't win, Salem," Ozpin said calmly, regarding the woman, "There are many ways in which a war can be won or lost. The tide of battle can change as easily as the waves of the ocean."
"Or like one's loyalty." Spat the woman, glaring at him. He did not wilt under her gaze, holding it firmly.
"Yes, I suppose one could put it that way."
"You would know, wouldn't you, Oz?" Her voice was calm again, and she descended her steps and began circling the Headmaster as he calmly sat there.
"Yes, you would indeed know that all too well. After all, weren't you the one who betrayed us?"
"I only saw the error of my ways, Salem, and took the matters into my own hands to end the suffering we caused."
"You betrayed us, Ozpin. You turned on us, backstabbed us, and ended what we started!"
Salem walked in front of Ozpin, and grabbed him by the hair, forcing him to look up at her.
"Humanity is weak, Oz. They are selfish and destructive. We were to unite Humanity together, destroy everything that made them weak and harmful to each other. We could have had peace."
The Headmaster calmly gazed into the witch's eyes, even when he was in pain.
"And at what cost, Salem? Creativity, individuality, freedom, self-expression, all of these make us Human. Without them, we would be nothing more than mere machines, not much different than the Grimm themselves. Would such a peace really be worth it?"
Salem released his hair, and stepped back. There was a foreign emotion on her face, as she looked at the man, as though looking past him.
"You killed her, Ozpin. She was everything to me, and you caused her to die," At this, her eyes hardened and she looked back at the Headmaster, "I cared more for her than I ever did for Humanity. So I will do everything in my power to crush them all.
You built up a long-lasting peace, Ozpin. I will not deny what you've done. Yes, through your betrayal, you ended the war we started, and brought a peace to the kingdoms that has lasted eighty years. So how does it feel, to see all you've done, everything you've built, be destroyed? How easy it is for your foundations to crumble? How do you feel?"
She was smiling now, and she knelt down in front of him, cupping his chin in her hand.
"The first phase of my plan has already been completed successfully. Soon the kingdoms will once again be divided, just as they were so long ago. When your smaller, more honest soul, eventually comes face to face with me, know that I will kill her, just like I did her predecessor."
For the first time, Ozpin allowed himself to get angry. He glared at the woman, and for a moment, Salem saw the man he had once been. A terror to his enemies, and even his allies. She might have even been intimidated, if he had any power here.
"What's the matter, Oz? Does the death of that woman still anger you? Are your nights haunted by your imagination, wondering just what I did to her? I bet they are. After all, I didn't leave a body to be buried."
"You robbed two innocent girls of their mother, and took a brave woman's life." He said, harshness creeping into his tone. But that was nothing compared to the outburst he was forced to bore witness to.
"And YOU took the life of the only other person I truly cared about!" Salem roared, her nails digging into the man's face, "Your petty little morals caused you to turn your back on us! YOU are as much a murderer, as much as monster as I am!"
She took a deep breath, and let it out, and withdrew her hand from his face.
"I wonder how they would feel, if those you cared about knew the truth behind you? What would they think of your dirty little secret? How do you think she felt, when she found out? That's right Ozpin, I told her all about you before I killed her. The look on her face. She valiantly tried to continue believing in you, even as she realized you sent her to her death.
It won't stop there. All of them, everyone you've put your faith into, they will all fall, cursing your name and wishing they had never followed you."
Salem turned and walked away, leaving Ozpin to sit there, staring after her.
Author's Notes: This WAS based off three theories I had, namely Salem killing Summer, her and Ozpin having been part of the oppressors of the Great War, and Salem having a sister, as the Wicked Witch of the East. But Volume 4 and the World of Remnant on the Great War have ruthlessly destroyed the latter two theories.