The small key in Astro Knights Island is for Mordred's secret hideout. When you come to that wind mill area, move the hay bales apart and use the key on that.
To push the haystacks in Astro-Knights, you have to get the small key from the fountain by pushing the crescent moon, the sun, the planet and the star. Then keep on pressing people until one gives you a small key. Run to the haystacks and STAND IN THE VERY MIDDLE OF THE TWO. The haystacks should naturally be separated at that time, and use your small key to enter the a small underground door.
you just click it.
There is no key to the dungeon. The small key open Mordred's underground laboratory, which has a back way into the dungeon. (see the related questions)
the door that's locked
The key unlocks the entrance to Mordred's hidden underground laboratory. (You will find it under two bales of hay.)
On a giant asteroid in the asteroid belt.
The key from the secret society opens Mordred's secret underground lab, under the two hay bales near the mill farm.
The secret room between the hay bales!
just click it.
it's in the astro belt at the bottom left coner area.you have to defeat the planets and have all the knights with you to get to the castle. once you have all the knights with you go to the astro belt then, go to the sword key and pull it out. after that you jump in the spining wheel thing.
do you know where the hay is at the same place you get the manure jump in the middle of the hay and make sure that you have the key from underground the small one