The common language is the agreed upon language of commerce around the world.  Because of this, almost every society in the world speaks it even if they also have another language.

History 

The common language came into existence in 38,396 TS in a small group of summoner encampments in the Lumarian Mountains. There were both elf and dwarf encampments which were constantly scwabbling about which race had the right to be in the area. One of the main problems that aggrivated the situation was that the elves and dwarves spoke different languages and very few people could speak both. This was long before ways of inturpretting different languages through mentus had been discovered so the language barrier proved to be a huge problem.

One day, a human arrived in the area. Though he seemed lost and disoriented, his presence actually helped solve the dispute between the dwarves and the elves. The stranger spoke a strange and completely unknown language called Anglis. After a while, he began to understand the difficulties between the two encampments and came up with an idea. He used their mutual language difficulties to mediate the problem. By forcing both sides to sit down and learn to communicate in his language, he was also able to bridge the gap between them and help work out their differences.

Because of the human's unique mediation efforts, the two encampments joined together to become what is now known as the city of [Eglictor], one of the longest lived independant cities in the world.

Word of the mediator's success spread and he was called into other areas to do the same thing. Soon the Anglis language had spread to various parts of the world and became more and more popular. Because of this, in 39,096 TS, the Fantasmal Government was finally able to declare an official language of trade and commerce. All of the various government representatives agreed to turn Anglis into the common language.

Note: The common language is almost identical to English on Earth.