The Cosmic Symbols is a pattern of Symbols that you will use to open a hidden passage on the Fountain in the Main Street in Astro-Knights Island. The order is: Crescent Moon, Planet with Rings, 5-pointed star.
How to Get the Cosmic Symbols
Go inside On the Ye Olde Rumour Mille and walk to the left and jump up on the hay bales. Then jump on the shelf and then up onto the gears and cogs. When you get near the top, jump to the right to land on a small platform in the middle. You will see a piece of rope hanging to the right. Jump onto this rope and this will lift the wooden rod so that it is no longer attached to the gears. Slide down the rope and you will land on a platform next to a very pale dark haired girl. Click on her. She will ask to trade secrets, and will take the secret message you found in the castle. In return, she will give you a piece of paper with three cosmic symbols on it.