Upstairs in the Cathedral you will find Eperdur. He will tell you that there is word of a foul wind coming from Gusgen Mines that is blowing on the Crag of Dem in Konschtat Highlands. The seal that stops the dead from walking is weakening. Eperdur gives you key item: Seal of banishing.
Travel to the Gusgen Mines. Go straight until you get to the first set of three levers. Pull the center one.
Continue on straight ahead until you get to the second set of levers. Pull the left-most lever.
Simply hug the left-hand wall until you come to a hole in the ground. Cast Invisible or use your Prism Powder BEFORE dropping down the hole - it contains bombs, which aggro sight and magic. Do not forget to cast Sneak or use a Silent Oil! The flies down the hole aggro sound.
There is a much faster and more straightforward path to this area than previously mentioned. Simply head to the northwest corner of the second map via right or left levers, and head down that small passageway, no drops necessary. Hitting the center lever is considered extremely rude, as it traps miners in that area with no access to the upper levels, and no way out other than warp.
The ??? is behind the shed to the southwest, located in (G-8). Deactivate Invis when nothing is looking your way, check the ???, and warp out.
Everything in this dungeon detects by sound except for the bombs at the end, which detect by sight and magic.
Level 50 and above will not get aggro from normal mobs.