Rarely used conversationally, Old Sylvan is mostly preserved due to traditional value and to read ancient written works. Training in the language is considered a mark of distinction among noble sylphs and mostly reserved for members of the higher castes.
Old Sylvan was obviously used by some common progenitor of the modern sylvan races. Naisylvan tradition holds that it was the ancient tongue of the noble sylphs, and that other sylphs descend from them. This is generally in keeping with the Bi-Imperial theory. Tri-Imperialist scholars mostly believe that Old Sylvan was spoken by an older, extinct race referred to as the Progenitor Sylphs. Certainly, Old Sylvan was the common language of a great empire at one point.
Old Sylvan is heavily agglutinate, with many distinctions indicated by compound affixes. It makes several consonant distinctions that are unusual in the languages of the Imperium, such as a wide range of velar consonants and aspirated/unaspirated stops. Some of these distinctions were discarded in more recent sylvan tongues, making it difficult for modern sylphs to become fluent in it. Speakers of other Imperial languages have even more trouble, especially because the language makes many letter transitions that are difficult for non-sylvan races to produce. There are very few fluent speakers of Old Sylvan who did not grow up with a first language from the Sylvan family.
Old Sylvan is written with a calligraphic cursive alphabet with an extremely shallow orthography. Letters universally map to a single phoneme, so once a speaker masters the handful of letterforms inscriptions are easy to decipher.
The alphabet has only five actual letterforms, using diacritics to indicate a total of twenty-three characters. This, combined with visual similarity between the letterforms, gives Old Sylvan an attractive, flowing appearance but a tendency to blend together. Modern sylvan writing systems universally make greater distinctions between letters, but Old Sylvan writing is widely considered to have a classical beauty that is lost in the translation.