Chapter 186
Cain exits the dungeon, keeping all his summons active and inspects the desert around the portal to ensure nobody has come across the location while he was busy. Nothing but unmarked pale sand dunes as far at the eye can see, as if the whole world was sun bleached.
This honestly seems like the best castle location they could have hoped for. There are dungeon entrances, an underground city entrance, nobody to bother them, and an abundance of building materials, also known as sand and stone that the Elementals can turn into a castle.
The more he looks around, the more of the dark colored stone he finds, the ruins of the old civilization brought either from deep underground or somewhere far away. Cain and his summons haven't found anything like it in the area.