The Ancient Tongue was once a unifying factor between all mortal races across Selaras. With the aid of their bonded Dragon
allies, to whom distance and language were no barriers, mortal language was shaped, simplified, and taught to all hominids beginning in the Golden Age. In this way, dragons and mortals hoped to bridge the gap of understanding, and thus foster peace between antagonistic nations. Many of the words in the Ancient Tongue were derived from roots in the draconic tongue.
It worked well for a time, and at the very least it allowed different cultures (human, elven, dwarven, demonic, nereid, aphyri, ifriti, etc.) to more easily communicate, barter, and learn. However, all unification progress that was made deteriorated after The Great War
. Post-war, when sea levels rose dramatically, the mortal races found themselves once again sundered: some divided, some isolated. Moreover, their draconic mentors were imprisoned -- distance, therefore, became an issue once more.
As ages passed, isolated peoples drifted further and further from the Ancient Tongue, with each different territory developing its own dialect, accent, and speech patterns. These differences were further exacerbated in the Eighth Age, when Allentria cut ties to all its former allies and closed its doors to trade and migration.
Though all modern-age languages on Selaras stem from the Ancient Tongue, and therefore retain varying degrees of similarities, some dialects have mutated beyond comprehension in more isolated parts of the world. Allentria, fortunately, retained much of the Ancient Tongue, even in its isolation, because so much of its recorded history was written in that language. Other large, powerful, or learned nations have remained close to the original unifying language for the same reason.