You underestimate his sense of possession. Lucifer is entitled. While you've insulted him, you've also reminded him that he isn't as omnipotent as he believes himself to be.

[A quick, ironic smile.]

Paradoxical, isn't it? How that simultaneously leaves him less dangerous and more dangerous. To you. [A beat.] You're right in that he'll want to push you around by means of egotistical balm, I am here to inform you that he will hardly stop there. It is more than merely making an example of you, Rincewind, by eradicating your free will he imposes his own. And what better way to conquer another entity than absorbing it?

Then who's to say you've ever bested him at all?