He felt it, the darkness in his heart. Derek wasn't sure what that would mean, for any of the three involved. If they felt it too, if it was because Stiles remembered more than they did of it, who knew. Either way it was worrying. He wasn't sure how to fight something like that, how to stop it, but he would figure it out. Mostly because there was no other alternative.
"So you did what had to be done and this is the consequence of it. That's something we'll figure out how to deal with if it becomes and issue. And really do you think I'd let you hurt anyone. I'll knock you the hell out until the crazy goes away and you know I would."
He wanted to know more though, he needed to. If this was going to be a threat in the future, or something that Lucifer could exploit... "You say you feel it, feel what? Its all a bit vague, darkness. You need to give me more than that if we're gonna work this out. I need to know if it's gonna go after Scott too." And he supposed the Argent girl but he wasn't about to throw his lot in protecting her completely just get. They were a work in progress.
"You might not completely trust my motives, who the hell knows, but here, facing what we are. I'm making it my mission to keep you all safe and you're better off just accepting it, alright?"