Substitution engine

A brilliant Alliance engineer invented these devices recently; they remain one of the Alliance Assembly's greatest secrets. Intricate gearwork inside the bronze-sided trunk allows the user to transform a message into a series of random letters. The holes in a wooden "key," which is custom-carved for each message, record the internal settings of the substitution engine; differently carved keys will result in messages that are scrambled differently. Only with the key, the scrambled message, and another substitution engine can the original message be reconstructed.

Substitution engines were designed be a high elf tinker. Thus, using one of the few devices currently in operation requires the operator to understand Thalassian.