Dark Speech

Dark Speech is the language of The Black Heart and its followers, especially the Dark Matter Vampires, Kenku, and Shifters. The language is deep, based almost entirely on throat sounds and heavily contextual. The written form of Dark Speech uses its own set of runes that ignore vowels and leave them for interpretation.
Dark Speech is one the Empowered Languages, the written form of the language is nearly completely unreadable unless you're a follower of The Black Heart and attempting to read it closely can damage your mind.