I have a few questions:
1. Is there a werewolf bad ending? If so, how do you get it???
2. What's purity do exactly?
3. Can I get a kiss?
Oh I can answer the first one. If I remember correctly, you have to continuously take the werewolf chief's side in every quest/option until he eventually asks you to go rat out two escapees, then you must let them escape once you get the chance.
After that, you won't be allowed to enter the werewolf den, but you *will* get an option asking if you really want to proceed. Selecting yes will throw you into a bad ending with the werewolves.