Once you are on the upper balcony. Use the switch and leave the room. Take the stairs up. After you reach the area, that is located outside of the dungeon, turn left and wall run on along the left wall shown in the above screenshot, and reach a chest with dungeon map in it. Return to the place that you started off from, and for a change, go to right now.
There is a series of the battles ahead of you. For starters, you will have to eliminate the undead tyrant accompanied by undead prowlers. Traditionally, for the battles of this kind, I suggest, to start off by killing prowlers, and leave the tyrant for the end. You should also be careful because the area in which you fight is not big, and that's what makes avoiding the monsters' attacks somewhat troublesome.
[TIP: in the meantime no checkpoints will be created, so you need to win all three battles without losing, or else you will have to fight them from the very beginning. As a result. I advise to play it safe and mind the player character's health points.]
After you win, go to the upper level and fight two defilers. The creatures have good distance. Attacks. What is even more. You will be receiving small damage for the whole time you're near them. Therefore, I suggest using the best of the attacks you have (I even advise considering launching the Reaper Form), to make achieving quick victory possible.
Step onto another platform and put up the last fight. There's a group of lichs to defeat here. Try and eliminate them, one after another and to keep spawns, summoned by them, at a distance. In this situation territorial attacks may prove very useful. After you finish all of the fights, explore all of the arenas and pick the items left by your enemies. You can now go through the western gate.
Once a new room, start by jumping down to the lower level. Fight the undead scarabs there, and have a look into a nearby chest afterwards. With the use of interactive creeper, return up. Initiate a wall run along the right wall shown in the above screenshot, and reach the vertical wooden pole.
Lean back and jump back, and catch onto another pole. Repeat that with the other poles, which will result in a safe passage to the ledge located at the other end of the room (the above screenshot). Enter the central area of the city of the dead again (of course, you are now on a different level than in the case of your previous visits), and watch a cut scene.
Since there is nothing interesting around (save undead scarabs), you can go towards the door to the West of here right away. Pass through a few narrow corridors, and eliminate opponents that you meet on the way. After you get it to a new room. Find the spot on the wall where it is possible to use the Death Grip (the above screenshot).
After you catch on to the interactive catch, let the player character perform additional vertical wall run, and only after that, bounce off the wall, and catch onto the vertical wooden pole (the above screenshot). Jump onto another pole, and then to the interactive edge on the left. Then, wall run along the left wall. Enter another area, where there is another puzzle for you to solve.
Start with positioning the death on the pressure plate seen in the above screenshot, and watch another cut scene that informs you of the changes in the environment that you may expect. As you probably have guessed you now need to activate Soul Split.
Send the first half of the soul to the left, to the interactive catch (the above screenshot), that appeared as a result of putting load on the pressure plate. Of course, you need to use the Death Grip and start moving right to reach a small balcony with the switch that unlocks the exit from this location.
[TIP: just like in the case of one of the previous puzzles, you could lead to the area now, but before you do, you may want to get access to the treasures described below.]
Switch to the other half of the soul and send it right. Make use of the interactive ledges and reach the chest shown in the above screenshot.
That isn't the end of what may achieve here. Terminate, Soul Split, step off the pressure plate and initiate this skill again. Position the first half of the soul on the pressure plate.
Switch to the other half of the soul and send it to the left using Death Grip to catch on to the catch. Keep catching on to the interactive edges, but stop at the edge that revealed itself as a result of putting load on the pressure plate (the above screenshot).
Switch back to the first half of the soul and step off the pressure plate. If you have done everything according to plan, the wall that the second half of the soul is clinging to should turn. As a result, you may return to controlling the second half, and start exploring the hidden area of the map (the above screenshot).
In the newly opened area, you can find lockers with weapons, a Boatman Coin a chest, and a GnoMAD's Gnome (the above screenshot). Connected with the side quests [GnoMad's Gnomes].
You may now terminate so that you, directing steps to the right and catch on to the interactive edges. Use the southern door shown in the above screenshot. Go south. After you reach the central room. Use the switch and use the Death Grip.