[ Forneus doesn't seem to react to being chided. Maybe he doesn't notice. ]

Well, the behavioural traits are the first to appear. If someone gets fully corrupted, their physical appearance will change to more monstrous. But when they've gotten to that stage, you can only put them out of their misery.

[ He folds his arms ]

The easiest way to keep tabs on the corruption spreading would to be have a divine to look out for it, since they can sense that sort of thing. However, you're a bit short on divinity out there, and I'm not permitted to leave this space.