Fallen

From FFa2Wiki

A very rare language, used by the creatures of the Southern Wilds, and a number of tiny island nations further south along the edge of the Southern Wilds. Fallen has a lot of hisses, clicks and glottal stops as well as some screeches, making it nearly impossible to decipher by other cultures, and is good for signals and giving complex orders in as few words as possible. This language seems to please the dead and the darker creatures of the south, and if used as a part of Shadow Magic or Necromancy, allows the caster to add their level in the Language Skill as bonus dice to the spell roll.

(Inspiration: 'Native' Tongues in South America)