You stand before a cryptic tower. On a locked door of crumbling stone is a strange cipher. The text is partially obscured by mold-covered cracks:
HOLLDW
SILENCE
BOUNLER
WASFUS
There are several keyholes and you spot five keys lying on the ground.
Unfortunately, each time a key is used, the internal pins are re-keyed. It will take several tries to open the door. Some keys will be used more than once.
You are not afraid to try your luck, for each correctly inserted key yields a clue. Yet take care… you are not the first who has tried these keys on the door.
The answer is a word related to the picture.
Text Version
(I think this is accurate but feel free to check my work)
Note that no information is obscured. If you cannot see a letter, it is whitespace.
TOWER HEADER:
VI VI IV V V VI VII IV
KEY 1:
FO
UN
NE_
RAL
KEY 2:
OE,Y
R
OHA
_
PY
LREI
DD
KEY 3:
WB
A
S
FNE
U
S
_
KEY 4:
LT
O
SUE
__T
(
5CEL
_
KEY 5:
S
_6T
U
LARM
OUNL
LSH
)SD
Helpful Questions to Consider:
"you are not the first who has tried these keys": Which key was tried prior? How do you know? What might that mean?
"several keyholes": Can you find them? How might they work?
Hint: The first "clue" begins with 'S'.
More Helpful Notes:
The mechanism is simple, though tedious, and can be solved by hand or in notepad. No computer required. How do keys and pins physically interact?
Hint: The second "clue" begins with 'W'.
Even More Musings:
1) I've been thinking I should hint that this puzzle will take forever to solve unless you make a key observation after working out Clue 1. It should at that point become apparent that a hash/mapping function exists, f(key)=n, whereby you can map each key to a unique integer, which can be used to have retroactively gotten the same result (clue 1) as well as later results in significantly shorter time than the 'mechanical' method. If on the other hand, you saw this right away and easily got Clue 1 but can't find Clue 2, it means you still need to work out what the 'mechanical' method was and how it is impacting the cipher.
Another Hint:
Text version of the puzzle has been added. Begin with key #4 to eject from the tower a six letter word beginning with 'S'. The key must go into one of the bottom four keyholes.
Visual Hint:
