The Stone of Time is an object needed to retrieve the Key of Hagith; it must be retrieved from the grandfather clock located within the antique shop. It is situated into a large pillar object inside the astrology room, in the Ophiel hall in Nowhere. To retrieve it, Harry Mason must first solve the Zodiac Puzzle to make it fall to the ground. The stone is then placed into the grandfather clock, allowing access to the Hagith key.
- Once the stone has been inserted into the grandfather clock, the clock will chime five times. This is a possible reference to the Clock Tower Puzzle in Midwich Elementary School, where the time on the clock will be 5:00 when Harry first enters the Otherworld.