You have to take the gold coin from the fountain and pay your admission to the Mordred museum. Get the Library Slip from the stack of books. Go to the castle library (first floor right) and to the bottom aisle, non-fiction, and press the shelf labeled Mc-M.
McM is the shelf label for the lower aisle of the castle library. If you have the Library Slip, you can press this shelf to open the dungeon passageway.
Once you have the Library slip, you can press the scroll McM on the lower aisle in the castle library, which will open the dungeon stairway.
It's downstairs. Press one of the stacked books with a paper on it, and it should get you the library card.
The library SLIP is marked "Non-fiction McM", which is the lower aisle in the library. Press the spot on the shelf marked McM.
In the castle library (first floor, right) there is a shelf marked McM on the lower aisle. Press it to open the secret stairway to the dungeon.
u just press on it
press the moon button then figure out the combination
Press launch
When you have used the golden coin from the fountain to enter the Mordred museum, and have the library slip, you can enter the dungeon from the castle library, On the lower aisle (non-fiction) press the shelf marked Mc-M.
If you have the library slip, press the brick over where it says McM. Then, go down the steps.
Use it to enter the Museum. Find the library slip in the stack of books. Go to the castle library (first floor right) and to the lower aisle (Non-fiction). Press the shelf marked Mc-M.
Get the gold coin from the fountain and pay your admission into the Mordred Museum. Once you have the Library Slip, go to the castle library (first floor, right) and press the shelf marked McM on the lower (non-fiction) aisle.