Nave is the third hub of Deathkings of the Dark Citadel.
Unlike the first two hubs, you don't begin this one in combat. Rather you start in a small antechamber before a large hall. The two doors in front you will both open when you open one.
In the hall is a very large number of Chaos Serpents and up on balconies a swarm of Dark Bishops, though the later are mostly ineffective at attacking the player because of the hall's architecture. They can all be prematurely alerted by firing a shot in the antechamber.
When you are ready, open the doors to the hall. Once you enter the hall the doors will quickly close behind you. Note this isn't an ordinary hall, at least for the monsters.
When a bad guy crosses one of the many pools of water, they are instantly teleported to another pool. This can make them difficult to keep track of and also makes the pools very dangerous for the player to pass over as they can be telefragged by a teleporting monster. The bad guys can't telefrag each other. Note that because of these pools, if you do alert the bad guys before opening the doors, it is extremely unlikely that they will all be bunched up behind the doors when you open them (there are pools of water just behind the doors).
In each alcove of the hall is an afrit and behind each stained glass window is a Slaughtaur and a Quartz flask.
At the far end of the hall are several north facing alcoves. Four of these contain switches that the player needs to press to open doors allowing them to access the aforementioned balconies where the portals to the hub's various sub-levels await, though groups of Ettins lurk down each passage. There are three other alcoves at the north end of the hub that each contain icons of all three classes' fourth weapons. However each one only contains two of them. Your main mission this hub is to locate the missing three icons and place them.
Head up the passageways up to the balconies and deal with the Dark Bishops if you haven't already. Each side has three balconies, the first and third ones contain portals, while the second ones on both sides contain a pair of panels that when opened reveal spinning gears. Each one has a gear missing that you must find and replace. Three of the gears you place will each allow access to one of the weapon icons you need to complete the hub. The fourth gear is related to unlocking the hub's secret map.
The weapon icons and the gears to open the passages to them are all found on the hub's sub maps that can now all be accessed.
NE: Hub 3: Chantry
SW: Hub 3: Cloaca — optional map, though completion is required to access the secret map
SE: Hub 3: Abattoir
Once you have all three weapon icons
Place them all and doors will open either side of the northernmost alcove (where one of the weapon icons was placed). Behind these doors lurk a few Dark Bishops and the portal to the final map Hub 3: Dark Citadel.
Accessing the Secret Map: Ice Hold Part 3
For parts 1 and 2, see the Hub 3: Cloaca map page. Now you have both books travel to the north end of the main hall. On either side of this area of the hall are a pair of walls with murals of a monk on them. These are in fact both secret doors that each lead to a small library containing a few Dark Bishops.
Note that several of the book cases indented into the wall in both libraries are openable and each contain a Slaughtaur and an artefact. You may wish to open them one by one now as soon they will all open at once.
One of the middle bookcases in each library will look different from the others. Also the spines of several of the books on one row of them will have letters on them. You must place the books you have collected in the gaps revealing that the row of books spell a word.
When you place a book all the other bookcases in the library will lower and the abovementioned indented bookcases will all open if they aren't already.
Once you have placed both books a message will appear on screen telling you that the doors back out to the antechamber are now open again. Return to where you started the hub to find a wall has opened revealing the portal to the Hub's hidden map: Hub 3: Ice Hold.