The "Purple Bull" Key is found in the document room on the first floor of Brookhaven Hospital in Silent Hill 2. It can be retrieved after reading a doctor's journal. It isn't shaped like a normal key, but rather a key card or a token, with notches cut into the bottom. There is also an image of a purple bull near the top, hence the name. The key is one of two needed to open the Louise Puzzle box found on a bed in Room S14 on the third floor of the hospital.