Unlock the corridor to the den
Given by Philip Tate, main hall (later in-game), Tate House
Clock Tower II: The Struggle Within
The Corridor Key is an item in Clock Tower II: The Struggle Within. Given by Philip Tate to Alyssa Hale, after she discovers the Golden Statue missing from Stephanie Tate's room, it is a required key to unlock the corridor leading to the den downstairs.
The corridor key can be found at:
Philip Tate (after the Golden Statue is missing from Stephanie's room).
Philip's dismembered arm (Ending K).
Bates finding the Corridor Key from Philip's dismembered arm (Ending K).