Klaus let out a bark of laughter at the mere thought of Jack helping to train anyone's slave. He nearly remarked that perhaps Katerina might be dead and out of his hair before the rise of the next moon were that the case, but then his dear sister came storming into the room with all her typical fury.
He stood to meet her, not blocking the slap or side-stepping it mostly because he hadn't for a second expected it. The shock in his eyes faded to a darkness few were ever unfortunate enough to see. His eyes changed and his fangs bared, but he made no move to strike his sister back.
"Yes, yes... Such a victim, Rebekah. Always a bloody victim. Have you forgotten that I killed him for you?" Klaus hissed. "Six thousand bloody years he hunted and tortured me as well, and our brother convinced me to make peace. Six thousand years!" The elder vampire's voice rose to a dangerous shout as he began to pace, fixing his sister with a look that managed to be both furious and wounded at the same time. He'd seemed to forgotten that Jack and his little slave were even still in the house. "And when you told me what he'd done to you? I murdered him without a second thought. And now this," Klaus spat, gesturing to Jack before walking up so that he was mere inches from her, looking down at her with the eyes of a man betrayed and enraged at such betrayal. "Brother plays with your little toy, and you dare to strike me? Do you expect that I'll do the same? That I'll hurt you or assault you? Do you think me our father?" Klaus took a step back, his eyes still boring holes into Rebekah's as he looked to Jack.
"No, dear sister. I would never strike you. There are other ways to chastise you for your betrayal," he said, his voice low and dangerous. In the span of a second he was upon Jack, aiming to wrap his hand around his childe's throat and force him against the wall. If successful, the other would plunge itself into his chest, gripping but not tearing out the other vampire's heart.