The air was thick with tension as Lucifer's words were spoken. He had been waiting for this day from the time he came into this world and that laid ahead of him, but there were a few things he needed to do before accepting her offer. She isn't stupid; there has to be some way that she makes sure I hold off my end of the bargain. (Yeah, it's for the plot, I know, and I am sorry for that.) So he stopped thinking about her and turned to the grand knight.
"I am now going to break the seal of your demon king."
(Wtf, that's extremely dark, if you know.)
"What? Why? What have we done to you to do this? And what do you even want from him?"
Lucifer tilted his head slightly, his ever-present smirk deepening. "Want from him?" he repeated, his voice smooth and cold. "I just want him to be out and free."