Third Floor

Collect the goodies (AR0203)

   This is basically one big room with two smaller rooms in it. In the north and the south are the Northern and Southern storage rooms. In the East and the West are the stairs leading back to the second floor. In the NE is the crematorium. Near that room you'll find a zombie from which you can take the leather straps, (which is as far as I know a useless item in this game).
Also get the sanctum key near the stairs in the West (you need it to open the gates to the first floor) and the prybar in the Southern storage room.

Fighting, or not

   Watch out for the dustmen, they will ask you what you're doing here, giving the wrong answer will let them call the guards. You don't want that so you can run or kill the dustman by snapping his neck, but you should have a sufficient high dexterity for that. When killing fails then you have to fight them. Don't worry you're strong enough, but it will make all zombies and other dustmen your enemy and you'll have to fight them to. It will give you extra XP's and different items, such as some dustman robes, which just might come in handy. If you don't want to fight tell the dustman that Dhall send you.
After completely exploring everything, you should have found a bone charm that is the key for the portal. The prybar you've found can be used on the skeletons to pry them open and get some items from them. One of them is labelled number 42, do you're prying on it and get your stuff back (250XP). There is nothing left to do, so off we go to the first floor.