"Yes."
And here's the part where Chrisor gambles.
He considers and dismisses the possibility of simply kidnapping him. Chrisor knows what torture is good for, and you can't get information from it, not reliably. They'll simply tell you whatever they think will get the pain to stop, whether it's true or not. Bun is clever, and he knows things that Cheliax doesn't. They want him creative. They want him to think about what spells to use to make defibrillators, or other fantastic things Chrisor can't even imagine. They want him to cooperate. They want him-- as much as it pains Chrisor to think it-- not broken.
Deception, then.
The task is to give him a view of Evil that they can maintain, through trained actors and censoring books and strategic use of illusions and mind control. Not forever; Chrisor is confident in his ability to tempt Bun towards Evil, given enough time. Bun does not seem sophisticatedly Good. He is no paladin of Iomedae. And Good, fundamentally, can't comprehend Evil; there are pleasures that Evil can offer that Good cannot even imagine.
But it has to hold long enough, and it has to make Bun enthusiastic about working with them.
He has some knowledge of Bun's psychology-- not enough, but some, Detect Anxieties and Detect Desires are his everyday tools and he is skilled with their use-- and he's made a study of Good people, at his time at the Worldwound. Bun seems almost monomaniacally obsessed with medicine. The thing to do is to give him an explanation that allows him to just do medicine, without thinking about it too hard.
Chrisor has only a few moments to think of it, and for months if not years they'll have to maintain the deception. If he succeeds, it will be the greatest deed of his life. If he fails, he will have all eternity to understand the depths of his inadequacy. (There are no excuses. Lack of time to think doesn't matter. The only option is perfection.)
It's exhilirating.
Chrisor briefly gives thanks for this opportunity to serve Asmodeus.