My bad, I didn't search for the context and it's not something i've encountered myself. Lets try this instead:
"This is it - the seal. It serves to amplify your fear and make you tremble in our presence. It makes you crave servitude, to debase yourself at your master's whim. Your master will drag you down to hell and you will follow without questioning."
Used our instead of my because it seems like any demon could complete the seal and any demon would have that effect on him. Using makes instead of "will make" as i'm assuming it has an affect on him even if it isn't completely activated; "will make" is more appropriate if it only does so when activated. The last line removes any question of agency for David. I'm assuming that the subservience invoked by the seal removes free will at least in so far as the inability to reject orders. I would imagine David would retain the capacity to not want to do those things as a further form of torture, as he would be unable to act on those impulses.
I don't think that sounds as overly erudite. Brutus is a gruff guy, but he's not dumb; otherwise he wouldn't be explaining the details in the first place. My writing would be more precise if I sat down and took the time to read all the various logic and conditions, but they're spread out over both Brutus and David's pages and keeping track of all those conditions is a challenge. As far as I can tell with a cursory look, it seems Brutus has feelings for David whether he's cleansed or not, so the scene makes sense in either case (though cleansed Brutus is a bit more articulate without all the pain clouding his speech). That's just my take on it, however. I can't claim to really have a full sense of either character because they didn't feature prominently in any of the playthroughs i've done.