The Dark Continent is a continent from where the Fanalis originate. It is the homeland of Morgiana and Masrur. Morgiana calls it Cathargo (カタルゴ, Katarugo). One can go there using ships from Balbadd. The side of the Dark Continent where the Fanalis live can only be reached by passing through the Great Rift.
The Great Rift got its name because sunlight doesn't get into the Rift, even though it should. This hints that there is a magical presence in the Rift. The Rift is so wide that one side is not visible from the other. Inside the Rift, one must be prepared to depend their life on their hearing and smelling senses, as the Rift is dark & vast.
The Dark Continent, Cathargo (カタルゴ, Katarugo), is based on the real-life region of Carthage. Carthage's Japanese name, カルタゴ Karutago, is the same as the Dark Continent's, but with the two middle kana switched. In addition to this, there are four further supports to the connection with Carthage. First is that Cathargo is located south of Reim (just like Carthage is located south of Rome). Second is the phrase "Dark Continent" and its description as it can be seen as a reference to Africa and its savannas or deserts (the Sahara specifically). Third, the original inhabitant on real-life region of Carthage (and all of North Africa at the time) were Berbers. Berbers were considered barbarians by Greeks and Romans (in fact, the words Berber and Barbarian are related) and this is likely the inspiration for the "wild"-nature that the Fanalis people are known for. Fourth, Berbers were often forcibly taken away to be sold as slaves or made into soldiers by other Medditeranian peoples (just like what happened to many of the Fanalis).