Bab 1232: "The Blood Clan Underground Kingdom's Exact Location" 

This is why people had to go through the abyss entrance or exit if they wanted to enter or leave the abyss. 

People also said that the abyss was so barren and a hell-like world, simply because it was a secondary world the same size as this world but with almost no resources. 

This proved the rumor that the demon race grew at an alarming rate until all the races in this world, including those in the dark camp, had to work together to seal the demons in the secondary dimension. 

It was said that all space-element ability users from various races, including the former Fairy of Space before Aetheria, sacrificed their abilities and lives just to open the second dimension and seal the demons. 

Nowadays, rumors about the abyss are varied and one couldn't just believe the rumor blindly. 

But the fact that no one had ever seen the place called the abyss, not even anywhere underground, means that the abyss might really be in another dimension.