this secret tunnel is like a vein to the castle.  It leads to many other rooms within the castle.  This includes passage to the dungeon, the throne room, the kings chambers, and a secret exit to the outside.  You must be careful because the tunnel is small to maintain its secrecy.  There are 5 different rooms to the castle that can be accessed through this room. This also proves as a good escape route as enemies with large armor will not be able to fit through.
Secret Tunnel, Inside Castle
king
thief
I am a thief that lives near the village. I pickpocket villagers and loot their homes when while they are away. I hate to fight and I am very fast to flee from danger.
Minding my own business! Indeed, you're the guards should be here any moment from now, I'll have your head on a stake by morning