Locked Doors in Two Quests
Collect a Trophy - In Wolfram's storeroom, there are two locked doors. The first door is by three switches. I flip all three in proper sequence, then press the button, and get the message "A door opens somewhere." The other door has a sign that reads "Only some may pass."
Disguise Yourself - The final door in Shapeshifter's Cave is locked. I couldn't find any buttons or switches. I tried wearing the wolf pelt cloak while holding the silver bullet staff, but that didn't help.