It's probably what he talks about with Lae'zel when she is trying to make a conquest for the evening ... I am jesting. I wish the tiefling party conversation with him was a little deeper if you save Karlach too, but I probably already wrote somewhere in this thread how much I like the chat you can have with him, if he follows Mizora's orders. It's a bit of a shame that we never get to explore what having defied Mizora and feeling the consequences - trauma aside - means for him. Wyll, similar to Astarion and Gale, has this thing going on that he on some level thinks he needs the warlock powers to get things done, even though they conflict with his ideals - and it just annoys me how much this theme gets buried if you keep Karlach around.
Edit: What I mean is - and please correct me if I missed something - if you have Karlach around you are suggesting to him that he needs to get out of his contract, but he never has a "this arrangement isn't working for me anymore" moment, does he?
He is weary of Mizora and mad that she tricked him into going after an innocent and he wants to get out of the pact, but he doesn't talk in length about it. He is a bit melancholic, but nowhere where he should be given, what he went through.
"We are all stories in the end. Just make it a good one."
