Collect three keys by talking to the Woodpecker NPCs while wearing the colour of paint that was gotten from the Paintbot in that area. West Forest is Silver, South Forest is Indigo and East Forest is Violet. This will open up a new area allowing you to collect the three keys to enter the North Forest. Enter the North Forest, ignoring the warnings and enter The Castle. Once you reach the Throne Room, follow the tunnel system downwards and downwards until you see something you weren't supposed to.