Vader could tell that somewhere in his dark heart, his Master pitied him. Thought it was a shame, what Vader had become; a beast more horrifying than any nightmare, but only because of how he appeared, not because of what he was. Only Sidious knew what Vader was like at the peak of his existence. All the rest of the universe had was the crude cave painting version.

Only Sidious knew what the universe had lost, aside from Vader himself. Only Vader knew the full horror of that loss.

Fortunately, that knowledge came with its advantages. Sidious would think of him as a lost opportunity and make use of what was left of him, believing that was all there was to do. Vader had learned enough of arrogance to foresee that. He would never have the power he had on the day of his turning again, but he was still alive and the Force was still with him. That had been more than enough when he was a child; he just hadn't known it back then. Nor had he known that good things always took time.

He was wiser now, and more patient, and he would wait. One day his Master would see the true Vader again, and while he wouldn't be the perfect beast of burden, there would be no end to nightmares he would unleash.