ToME WikiYou can get the quest by entering the quest entrance in Khazad-dum. There is currently no way to get the quest and its difficulty level on your list before you are in the middle of it.
To take this quest you should be powerful enough to take on many non-unique greater demons of the worst sort, such as pit fiends and greater balrogs, since that is what you are going to face. Durin's Bane is a sissy compared to these guys. You are likely to end up having to kill many more than the initial number of demons for reasons of chain summoning.
Mountain climbing ability is a great advantage in this quest since the walls are all hard rock. You can retreat to the walls to heal and you can stand in a wall to minimize the number of enemies you are fighting at once.
The reward of extra house is of little value since the location is so inconvenient. However, because the demons drop good loot, the quest can be its own reward for a powerful character who gets lucky.