Vetus was an ancient language of Signataria and Signatio spoken by the Insignis race of the Atonement Era. It was a common language until it was derived and replaced by Litera by the modern era.
As the Insignis race were originally angelic-like beings who were servants of the gods, they possessed an innate ability to speak a special language that can only be understood by their brethren. Their ability was retained after their descent as the fully-formed race, serving as their second language alongside the Common tongue.
However, as the communication between races became more complexed as eras gone by, the race needed to refine their language which was readable and understandable enough for other races to learn. Combining the Common language used mostly by Humans, they created a new language that combined both it and Vetus using the Common alphabet. They eventually named it Litera.
As the Insignis and Signatio began to use Litera, Vetus slowly began to fade into obscurity as years gone by. Eventually, by the Shadows Era, Litera became the country's main language. Yet wanting to preserve the history of Insignis's history, archivists started to collect any reading materials related to the Vetus language. By the time the modern era came, it became an ancient language that many eager historians are willing to learn. There are some groups and organizations in Signatio that used Vetus as part of their tradition and culture. Some of them along with the Mana Guardians used Vetus as the basis of the cipher language, Symbol Speech.
Not as much is known about the alphabet. But according to historians, they have the same lettering design as with the current Litera alphabet. The alphabet was also the inspiration behind the mysterious Symbol Speech.