G.U.E. Coal Mine #502, located south of Bozbarland (in fact, the amusement park's flume travels through it), was managed by Ernie Flathead. While the large mine was most likely abandoned when the capital was moved from Egreth to Flatheadia in 771 GUE, the mindless troglodytes continued their rote tasks, working without masters as though they were robots that had never been switched off. Before being abandoned, one section was sealed with a heavy door guarded by laser beams, thousands of flying daggers, and a hundred vicious kobolds.

In 957 GUE, on a quest to rescue Belboz from Jeearr, an unknown sorcerer passed through here, making several changes along the way: the presence of the human was enough disturbance for the mine entrance to collapse, thus making the air unbreathable with a build up of coal gas; the combination lock on the door was broken, permitting entrance to the closed off sector; and a secret scroll was stolen.

SOURCE(S): Sorcerer