Qualith

Qualith was the written language of illithids. It took the form of four parallel lines that had texture that conveyed meaning when read by an illithid scanning its four tentacles along the lines simultaneously.

The script was imprinted psionically onto the surface and transmitted the thoughts of the mind flayer that had inscribed it to the reader. It could be written on parchment, in books, or carved into surfaces. Degradation of the material could cause the message to fade over time.

Qualith was extremely difficult to read for non-illithids and usually required magic such as a comprehend languages spell to decipher because each of the four lines of script modified the others and only when taken as a whole was the full meaning understandable. Readers attempting to non-magically decipher the message, if successful, could gain insight on the writer's thoughts, its meaning, and even who the message was intended for. Failure, however, could drive the reader mad, or at least with a bad headache.

Some specially trained dwarves known as caradhakers (which loosely translates to "mindstalker") were said to be able to grasp the basic meaning (but not the nuances) by running four fingers over the striations.