Dark Tongue

The Dark Tongue, sometimes called the Black Speech, is the language of Chaos, spoken by its servants and followers. It is the only language that can adequately express the mysteries of Chaos, capturing the mystical and the arcane in ways that no other language can. While similar in some ways to Daemonic—the magical language used for casting Chaos spells and rituals—Black Speech lacks the magical weight found in the other more blasphemous tongue. Speaking the Dark Tongue does not (always) attract the attention of the Dark Gods, nor can it be used to speak the incantations needed to cast a spell or recite a ritual. The Dark Tongue is also a root language for others spoken in the Old World and beyond.

Queekish is ultimately a bastardisation of the Black Speech, polluted by mispronunciations and injected with squeaks, trills, and other sounds, since the Ratmen lack the mouth structure to enunciate the words properly. Also, the Dark Elves of Naggaroth speak a related language called Black Elven, which blends the lexicons of Eltharin (the tongue of High Elves) and Black Speech, though they use pure Dark Tongue when discussing matters related to sorcery.

As mentioned, the Dark Tongue is rich in phrases and words that express the complex nature of Chaos. Many make the mistake of attributing basic meanings to the words, but each holds far greater meaning and significance than a translation can supply. Each word encompasses a broad range of concepts, each with a different connotation depending on their arrangement with other words in the language and the addition of prefixes and suffixes, revealing different and deeper meanings held within the root. And, of course, mutating the root yields even more meanings.

Though the individual words have incredible depth, there are far fewer words in the Black Speech than in many other languages, though the root mutations as well as the addition of prefixes and suffixes allow innumerable variations. Thus, few speakers of the Dark Tongue know the language fluently or learn the many secrets it hides. As a result, this tongue is an effective means of expression for occult lore.

Chaos Runes
When written, the Dark Tongue uses Chaos Runes. These inscriptions can be found in everything related to Chaos, from banners and the Chaos Monoliths that demarcate the boundaries of the Chaos Wastes, to the hasty scratches on Herdstones, etching on weapons, and marks on shrines and temples, daubed in blood or dung. Chaos Runes are distinctive, readily identifiable for their character; there is no mistaking a Chaos Rune for anything other than what it is.

Chaos Runes represent ideas and experiences. In a sense, these Runes are shorthand for more complex phrases. A single Rune could represent a mutation or even mark a place of significant pools of Dhar. It’s believed there’s a single rune for every mutation, every change that has ever existed and will come to be. Many creatures blessed by the Dark Gods also discover these odd Runes pressing against their flesh from within. Hidden Mutants may cut these symbols out of their skin to preserve their cover. Hence, extensive scar tissue makes Witch Hunters suspicious.

Phonetic Runes
Chaos runes are represented by phonetic runes. These are used just like letters, forming words and phrases based on their arrangements. The runes are evolved from the Daemonic phonetic runes used in scribing spells and rituals. Such writings are highly sought in the Empire and beyond. Witch Hunters and other agents of the Cult of Sigmar seek to destroy these writings, while cultists covet them for the secrets they contain.

Source

 * Warhammer Fantasy RPG 2nd ED -- Tome of Corruption (pg. 110).