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. It could be written on parchment, in books, or carved into surfaces.

Qualith was extremely difficult to read for non-illithids and usually required magic 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. 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.