It's called a black hole, and it really is a pitch-black hole.
The walls of the cave are mostly made of bricks and stones. These bricks and stones are different from the Star Color Stones outside; they are a rare type of Limestone. This kind of stone can be polished into an Array Plate, and can accommodate most Intermediate Rank magical energy arrays, as well as some simple High Order magical energy arrays.
Materials that can accommodate High Order magical energy arrays, whether it's parchment, stone, or demonic materials, are very expensive. And here, the walls are entirely composed of this Limestone.
If Angel can notice the difference in the stone, naturally, others can too.
Except for the Black Earl and Angel, everyone else had a bit of a covetous thought but were too embarrassed to speak up, except for Dox, who unabashedly said, "How about you guys go ahead, I'll dig up some stones and catch up."
After Dox voiced his opinion, Kaier and Vay seemed eager to try.
