The password for the secret society is a group of Cosmic Symbols. By pressing the three symbols (and the sun) on the fountain's brass plaque, you create an opening to a secret meeting place.
Once you have the Princess's Secret Message (castle, first floor, left), you can get the password from the girl up in the hay loft of the Mill.
Done!
You do not get or use a bucket on Astro Knights Island.
There is no treasure chest on Astro Knights Island.
There are no bird eggs in astro knights island.
its on the island
How do you talk to the girl in the hay loft at astro knights island?
There is nowhere to enter a password. Fix the saucer and get the coordinates you need to fly it. (see related questions)
On every island you have to be the one to save whatever needs saving. That includes the kingdom in Astro Knights Island.
Once you have built a new spaceship on Astro Knights Island, it will park on top of the castle whenever you leave the island.
on astro knights island
With Mordred
Astro Knights