Deep Speech

Deep Speech is the name given to the way that creatures like the mind flayers communicate. The language does not consist of words. Those who use deep speech communicate their thoughts and emotions directly from mind to mind.
Because of the way that Deep Speech is communicated, those who use it do not have a written script. However, the humanoid races that have experienced Deep Speech have devised a script using a mix of pictographs and Dwarven runes. It is rare to find someone who knows how to read or write in Deep Speech and unlucky to find one that speaks the language.