How long until his heart breaks?

The nogitsune may be gone but what if he had left something behind in Stiles, something dark and evil that only Stiles knew about. Stiles tried to hide this part of him from the pack. He wanted everyone to remember him as the happy sarcastic boy everyone knew and loved, but the pack only saw him as a liability; a weak addition to the pack. So what if a villain took Stiles to get back at the pack and the only way he could escape was to embrace his darkness. Would the pack change towards him and how much would this impact Stiles?