Arkaylia is the name of one of two artificial moons that orbit the moon of Mongo. Along with its brother moon Surd, it was created pre-Great Sorrow for the use of shelter for travelers that came to mine the moon for its riches. Arkaylia was also used as a place to process the Zerilium that came from the moon.
Immediately after The Great Sorrow, a group of Mongo inhabitants were chosen to leave the planet and live on Arkaylia. And they did so for three generations before going back to live on Mongo.