Languages of Veth
Ankenah is less a language and more a magical system! Created by Tekhem "Ankenahotep" as-Tyrakhon, this system of glyphs aims to distill the essence of the world and universe into linguistic forms. Its daughter language, Najjira, is the native language of the Najjira people.
Better known to us as English, this is the most commonly used language in both BDI and in active play in general.
Spoken widely in Griffon's Aerie and in any place where its people congregate, Griffon is quite commonly heard in both Drache and any other large port town.
Several of the languages of Veth have been given their own scripts. Languages with bolded names have (a) usable and learnable writing system(s).
Ankenah, the magical language which spawned modern Najji, originally used a set of ideographs to try and capture the essence of the universe in order to distill it into something understandable and usable by human beings.
Arangothek has its own writing, which you can see explained here.
The Assi language apparently uses a system of ideograms.
The desert-living Teldanar use an as-of-yet-unexpounded-upon heiroglyphic writing system.