@JeremyECrawford I can't seem to find any info on how Deep Speech actually works; could you help clear this up please? Is it telepathy?
— Orannis (@Orannis0) May 17, 2017
Deep Speech is a language (see PH, 123). You speak it. #DnD https://t.co/t1VNE7Y42V
— Jeremy Crawford (@JeremyECrawford) May 17, 2017
Deep speech is the language of Aberrations and cthulian horrors, chief among them from the perspective of humanoid races are the Minflayers and Beholders. From a language perspective, the language is often written in Elvish as it was first documented by the Drow and other denizens of the underdark. I like to think of it like a gutteral popping and slurping sounds as if an octopus was out of the water.
Great answer Alex!!! MUCH better than Jeremy gave by the way.