The Black Walls are a feature that can be found inside The Maze, that constantly change position over time. These walls are used to give more of a challenge in reaching the Cavecrawler Cavern, by blocking seven available routes to reach the cave, and only leaving one for the player to go through.
The Black Walls are large in height, and are colored deep black, with a "Plastic" texture. These walls are unable to be blown up or removed in any way.
If an exploited map or video tutorial of the path to Cavecrawler Cavern is leaked, then Defaultio, on rare occasions, will personally close all seven walls to the Cavern or worse, block the entry to the cavern with a stone wall.