Suloise
This ancient and widespread language became all but extinct after the Baklunish-Suloise War destroyed the Suel Imperium. Today it is rarely spoken, even by the few scholars who know the tongue. The infamous Scarlet Brotherhood are one of few that continue its use. It exists in its written state for those who would delve into the surviving arcane tomes of the Suel people. Transliteration into modern tongues or alphabets is difficult, and dangerous when used in spellcasting, for the significance of certain inflections has been lost over the centuries.