In Paracelsus's The Third Defense: all substances are poisons; there is no substance without toxicity. The distinction between medicine and poison lies in the proper dosage.
Even a deadly poison like aconite could be used as an ingredient in Wolfsbane Potion if properly handled and carefully dosed.
But mastering that dosage required extensive experimentation. Cecil had also wondered what happened to the werewolves the Werewolf Capture Unit sent to prison every day after catching them.
All sorts of dreadful speculations left the Werewolf Capture Unit, working under such intense pressure, uneasy and anxious. Though his time with his nephew was brief, Cecil could temporarily put those matters aside. They arrived at Flitwick's Charms classroom, and Cecil found the seat where he used to sit during lessons.
Cecil's grades had not been particularly outstanding when he was in school, at least not like Gilderoy Lockhart's extraordinary talent. Lockhart had actually thought of using the Humanizing Charm to temporarily turn werewolves into human form to deal with the Wagga Wagga Werewolf.
Cecil had once consulted Lockhart at a seminar. Lockhart said that the Humanizing Charm was extremely complicated and required pointing one's wand at the target's throat. Moreover, the Wagga Wagga Werewolf was not exactly the same as the Lycan clan. So Lockhart politely declined Cecil's invitation to join the Werewolf Capture Unit in hunting werewolves, then promptly went abroad for new adventures.
The unusually long Christmas break was also related to intelligence Cecil had received. The werewolves had originally planned to launch a surprise attack on Hogwarts on Halloween, but that day was the last day of the Full Moon. Most werewolves had already transformed and were in a weakened state, so they decided to act at Christmas instead.
This group was called the Blackbacks because, after transforming into werewolves, the