On the one hand, there was a path to indulge. He needed it—there was no doubting it. How could he pass up a chance to grow almost three times more powerful than he was now, knowing the kind of danger he was going into?
But there was no mistake about it: he would be indulging. And maybe this would even open up a path for the Lust Seed to begin influencing his mind more than it had been capable of before.
And then there was the other… to ignore this chance entirely and use the Duchess as a puppet instead.
Of course, this came with its own dangers. Setting aside Sylas' own inner struggle with his Pride and Lust, if he didn't fuck the Duchess, Compelling Gaze's effects would begin to weaken. To make the cognitive dissonance the strongest, it was a necessary part of what he had to do.
That said, Sylas should be able to use her for long enough to get what he needed the most: information.