The strange device is an item obtained during the Ritual of the Mahjarrat quest. To get this item, you must search the rubble on the north side of the largest island. You will find a tetrahedron among the rubble.
When "Check-output" is selected on the device, a four letter code containing letters A–H will be given. Each code corresponds to a particular location, similar to coordinates. The first two letters correspond to the east-west direction, and the last two to north-south direction. For these, moving from A towards H is moving east and north, respectively.
For the two letter code for both directions (ie for both the first two letters and last two letters), the code changes at the second letter first, until reaching the end of available letters, at which point the first letter changes. For example, codes moving east from BDAA would be BEAA, BFAA, BGAA, BHAA, CAAA, CBAA, etc.
The device is only useful once all four tetrahedrons have been found and placed into the indentations in the walls of the underground chamber. Once this has been done, the letters on each of the tetrahedrons will form a four letter code. Players will need to find the location with the matching four letter code and dig at that spot to find a Kethsian key.
This information has been compiled as part of the update history project. Some updates may not be included - see here for how to help out!