Drow

An unholy marriage of Aeonesti and Demonic, the common tongue of the Abyss, Drow is an extremely complex language of vast contrasts, at once elegant and terrible. It is therefore nearly impossible to learn for non-native speakers and is never taught to non-Drow, a transgression punishable by death in most Dark Elf societies. As a result of highly secretive and deceptive nature of Drow culture, rife with clandestine intrigue and assassinations, the language has developed an intricate and perfectly expressive system of hand signs, which differs slightly city to city, house to house (to maintain secrecy), but also with a common form understood by all Drow.
The language itself uses the Drow Alphabet within Dark Elf cities and fortifications, but Undermarks when traveling through the endless tunnels and caverns outside their homelands.