Tuvai

Tuvai is the most widely spoken human language (or language family, depending on whether its many dialects are considered separate languages) used in Urva. It is the native language of a majority of humans across Orithea, Rhydain, Taijuria, and the Western Isles, and is often referred to simply as "Common" or "the common tongue" throughout those areas. It is sufficiently widespread across a sufficiently vast area that it is the most common second language even for those who don't speak it as their native tongue, and thus also serves as a lingua franca or language of trade for merchants and travelers in non-Tuvai-speaking areas. A Tuvai dialect is also spoken by the aristocracy of the Sarcian Empire in northern Achuirea, although not by the lower classes there. The various Tuvai dialects are at least mostly mutually intelligible; a Sarcian and an Azhirite may have some trouble conversing fluidly, especially about subtle or complex matters, but they are still speaking variants of the same tongue and can probably figure each other out after some missteps and confusion. 
Alphabet: Common Tuvai is usually written with an alphabet of 28 characters, although there is regional variation and in some areas more or less characters are used; such variations often reflect the absence of particular vowel sounds in the local version of Tuvai, or the need to denote peculiarities of the local dialect or pronunciation with extra letters or markings. 
High or Priestly Tuvai is a highly formalized variant of classical Tuvai, used as the liturgical tongue and language of sacred writings by the priesthoods of the Thaedonu-Vaati. Unlike the standard version of the tongue, it is always written in a strictly preserved 39-letter alphabet (39 being 3 times 13, numbers of divine significance in Utara-Vaati). Grammatical structures and pronunciation in High Tuvai are held to exacting rules which have been unchanged for many centuries, in contrast to the common dialects with their great variation, plethora of slang and colloquialism, contamination with foreign loanwords, and so forth. The average Tuvai speaker can understand the priestly dialect (they will have heard it countless times in religious ceremonies and so forth), but will struggle to speak it fluidly and correctly; proficiency with it marks out the speaker as a priest or priestess, or at least an accomplished religious scholar. 
Ancient or Archaic Tuvai
A proto-archaic form of Tuvai is supposed by scholars to have been the original language of the first humans, the Unbegotten Men, taught to them (according to lore) by the god XXXXX. Of course those times are lost to the mists of ancient history, known only through myth and legend now 
Aside from Tuvai, the major languages spoken by humans of Urva today are the Daare Karsha tongues (the various tribal languages of the people of the Kesh Karkhan), Suaga (the language of the Suagirs, itself possibly a variant of the Daare Karsha group, since as the distant ancestors of the Suagirs may have been natives of the Kesh Karkhan before emigrating down to the steppes), and Chomarra, the language spoken by most humans of Achuirea, including the common classes of the Sarcian Empire. Other groups with their own distinctive languages include the Vards, the Thelbirs, and the XXXXXXX. All of these languages ultimately derive from archaic or proto-archaic Tuvai--necessarily, since that was the original tongue of all humans--but they diverged from it so long ago, and have changed sufficiently over the millennia, that they are now completely different languages with no chance of mutual intelligibilty.