Proto-Plains is the name I gave to the proto-language that gave birth to the Dothraki and Lhazareen languages. It's not fully developed, but I did develop a method for deriving vocabulary for Lhazareen (and even went a little bit into developing its grammar). Unfortunately, given the scope of the book series, it seems unlikely that there would ever be a need for a full Lhazareen language, which is too bad. As I've conceived it, it'd have vowel harmony and lateral fricatives. Anyway, one day I may flesh out Proto-Plains so others can derive sister languages to Dothraki (or their own version of Lhazareen), but that day won't be coming soon.