The Astrolabe Room
Centered inside this circular library room, 9m in diameter, there is a golden astrolabe. It has a myriad arms of brass holding up beads and panes of glass, each carved in impossibly precise patterns. The arms are controlled by two heavy interlocked gears, 45cm or so in diameter - the heavier top gear can be set into one of four possible positions, while the smaller bottom gear can be set into one of forty.
The gears can be rotated in unison to set the astrolabe in specific configurations by moving the arms around it's surface, but the bottom gear is damaged - it unshackles from the mechanism when the top gear is set into it's fourth position. In this unshackled state, the bottom gear can be manually set to any of it's 100 possible positions.
Inside the machine, lies an unlit tallow candle. When the candle is lit, the light filtered through the glass beads projects images on the walls of the room:
When the top gear is set into the 1st position, the bottom gear is automatically set to the 11th position, and the scene projected is that of a lone Knight with his shield up high, defending against the fiery blast of a Dragon. There are 11 lit stars visible in the background.
When the top gear is set into the 2nd position, the bottom gear is automatically set to the 22th position, and the scene projected is that of two Dragons laying siege to a lone Tower built on the edge of a precipice. There are 22 lit stars visible in the background.
When the top gear is set into the 3rd position, the bottom gear is automatically set into the 30th position. The image projected is that of three Dragons flying in a circle. There are 30 lit stars visible in the background.
When the top gear is set into the 4th position, the bottom gear unshackles from the mechanism. The image projected is that of a Knight, longbow in hand, opening fire against a Dragon from the top of a tall, burning Tower. No lit stars are visible in the background.
Setting the bottom gear manually to any of it's 100 possible positions projects that many lit stars on the walls of the chamber.
If set to it's correct position, the Astrolabe will unfold to reveal an eyeball-sized glass bead hidden underneath it's central golden-brass plate. The bead is delicate and even more exquisitely carved than the others, worth 500gp on it's own to a collector of exotic goods or illusionist. However, if a character replaces one of his or her own eyes with the glass bead, it will filter the light of the Moon into patterns that reveal to the user the ways to an ancient empire of wondrous technology and magic, swallowed by the Sea.
The Astrolabe itself, including the minor beads, is worth 1000gp if transported whole (it weights 2500 coins), and the glass beads are worth 250gp by themselves.
Solution
- 1 Dragon + 1 Knight = 11
- 2 Dragons + 1 Tower = 22
- 3 Dragons = 30
- 1 Dragon + 1 Knight + 1 Tower = ?
Solving for the Dragon:
- 1 Dragon = 30/3 = 10
- 1 Knight + 10 = 11
- 1 Knight = 1
- 1 Tower + 20 = 22
- 1 Tower = 2
Therefore
- 1 Dragon + 1 Knight + 1 Tower = 10 + 1 + 2 = 13
Setting the bottom gear to it's 13th position manually solves the puzzle.