I've talked to the ghost in the room on level 13, and I've long since completed the quests in Heritage Hill, so I should know the ancient language (I do remember learning it). According to everything I've found, I should have the option to get through door on level 13, but it's not giving me the pass phrase option. I'm only getting the "I'm the rightful owner" and "I'm looking for the master below" options.

 

My save file is here: https://drive.google.com/open?id=0B9oqa9KBpiHKcXFjcDNMUUFHWVk&authuser=0

 

 

That door requires that you first try to open it then go talk to the ghost in the far NE area again.  When you talk to him the second time he gives you the oath that originally opened the door.  Remember what the spirit breaking the machine said about turning the guardian souls against Nua?  That is one of the dialogue choices that you'll have after returning to the door.

There are 4 spirits in the area, and if you talk to them to find out some proper information you should be able to make your way through the door.