Sustätyes is the language of the ancestor peoples to the current people of the Kingdom of Fortuna. The city of Blackport, currently the capital of the nation, is the site of their old City-state, Voltunwe (meaning the Life of Fate). These people were often attacked by raiders and people from other nations, and needed to work together in order to keep strong. Legend has it that these people, the Voltunsus (Fated People), living in Voltunwe, suffered from a period of much violence within themselves that nearly spelled their doom. To combat this, they developed an extremely sophisticated--and since lost to the ages--system of justice. Apparently this system quickly dispelled most, if not all such activity very quickly, allowing the focus to return to the pressing matters of foreign raiders.
As a result of this Justice system, the dichotomy between truth and falsehood became a very important concept to the Voltunsus. Telling a malicious truth was bad, but a malicious lie was worse, a comforting lie wasn't all that bad a thing to do, but if one could tell the whole truth and still be comforting, that was even better. Such comparisons are at the heart of Voltunsus culture, and therefore their language.
Having been continually used for legal purposes since the advent of the language until the present, much is known about the language, even (unlike the Latin of Earth and the Roman Empire) the phonetics and pronunciation rules survive until this day.
Less is known, however, about the daily activities and culture of the Voltunsus. For example, it is known that they were monotheistic in their primary faith, but the nature of their god is unknown. It could have been a many-faced deity just as easily as one with innumerable servants that ran different aspects of the world or a god that resembled Earth's Abrahamic deity of Christianity, Judaism, and Islam. About five hundred years ago, a new faith emerged, through some combination of evangelicalism and revelation, resulting in the destruction of the old, now heretical, texts.
Also, it can be assumed, as the city of Voltunwe sat on the coast, with extensive waterfront access and a very useful anchorage, that a good deal of the City-State's economy came from marine occupations, but whether that was more fishing than trade, or vice versa, is almost entirely guesswork by modern historians and archaeologists.