Akkadian

Witches are special in many ways; their lack of a true ego form is a great weakness, but therefore they have many other strange talents and mysterious ways to go about their unrivaled magical abilities. One thing that sets them apart from other Sinners is, that whenever they cast a spell, enigmatic runes start glowing under their skin in the resonance color of the spell that's being weaved.
While this phenomenon can be subdued with conscious effort and training, it is inherent to all Witches and Warlocks like a birthright or curse; and strangely these signs and characters are universally the same on every witch, but show up in different patterns depending on the spell. How exactly they are appearing seems to be tied to the condition of the spell cast, the nature and allegiance of the witch and her Daimon with some other contextual factors thrown in.
Scientists and cultists have researched these runes for decades and have come to the conclusion that it is in fact a language of its own.
The Praharian Hermetic Tereza Polanski published the first type set of an Akkadian alphabet in 266 CoMa. It has since then constantly been revised and altered and has become a comprehensive language for scholars and cultists to study and express the Arcane arts in. Additionally, the knowledge of Akkadian can indeed help with identifying the spells an opponent is casting.

Writing System

The Akkadian alphabet is a curious thing, featuring characters more than letters. Crescents, lines, dots, wedges and other geometrical shapes come together in fluent combinations and mean different things, a cuneiform of secrets. These symbols are associated with semantic meaning but the context is lost, so scientists are puzzling it together by conducting tests and experiments with witches casting certain spells and then looking at the resulting signs.

Phonology

There exists no common ground on how to pronounce Akkadian - it's not a spoken language after all. That doesn't stop especially dedicated circles of witchcrafters and weavers to try and express themselves in this language verbally; but those standards are just local color, agreed upon by isolated groups of people.

Arcane Language of the Weavers.