Ak’tah’ya

This ancient language is believed to be one of the oldest in existence. The dwarves claim it is the language spoken by their creator long before mortal creatures roamed the world. Clerics of the dwarven deities claim that modern dwarven is a lesser form of ak’tah’ya, though even amongst the clerics the only ones who learn ak’tah’ya are the Voices of Wisdom.
More akin to telepathic communication than modern spoken languages ak'tah'ya uses incredibly subtle changes in inflection and tone to communicate a wealth of meaning in a single word. To the untrained listener it can sound like speakers are just repeating a sound over and over, when they are infact communicating a huge amount of detail in very words. The language is so different to regular written and spoken forms of communicaiton that regular magic is unable to translate it. The Voices who learn the language have to undergo special training and magical enhancement of their hearing and sight to be able to understand it in a process that usually takes a decade to complete.
The written form relies on runic script akin to dwarven, but with a greater emphasis on the exact shape and thickness of each line. Almost imperceptable differences in a line can completely change the meaning of a word so regular writing or carving are not up to the task of recording it. Only magic is capable of recording ak'tah'ya and it is typically carved into stone slabs using a spell to shape the stone. When properly recorded reading this language provides the reader with an insight into the writer's mind as if they can not only read the words but the intention behind them. This makes information recorded about crafting skills incredibly useful as it can be like watching the writer perform the skill.  It can also cause problems if the writer is recording a traumatic event or doesn't really understanding what they are writing.

Are you sure that's supposed to be a language?  All they're doing is saying hmm-da-ka at each other.