The entrance to this zone is actually through a sewer pipe on the cliff face at 362.5,178.6,-133.3, it is easily spotted by the trail of luminous green sludge pouring out.
Woglok hits fairly hard. At 75% health, he animates his left knife. At 50%, he animates his right knife, and at 25% he animates both knives at once. The knives cast a minor uncurable debuff as long as they're up, and are relatively easy to burn down.
At 90% health, Va'Tak summons a purple mist that covers the floor. This mist does significant damage over time. To follow the script, look to the ceiling once he summons the mist and click a glowing light to temporarily banish the fog.
You can also try to fight Va'Tak by standing on top of the stacked crates above the fog. However, if you try to fight him like this, Va'Tak will cast "Symptomatic Dementia" - a stacking debuff that decreases your potency by 25% per stack. Symptomatic Dementia can be interrupted.
Shograh has some sort of AOE, but keeping her near the grimling corpse you can see her drawing power out of before you begin the fight seems to prevent her from summoning adds. If the adds don't spawn, she's tank n' spank.
- After you kill Shograh click on the East and West Gate House Switches to open the gates to the area to reach Sa'Dax Senshali.
Sa'Dax will periodically throw shards of Dark Luclinite on the ground. Click them to remove them. If you aren't fast enough, they explode, doing fair damage and a knockback.
At 75%, 50% and 25%, Sa'Dax will teleport into the air leaving 3 colored spheres (red, yellow, and blue) behind. An emote of either green, yellow, or purple will appear on your screen, and you have to click the two spheres that combine to form that color (e.g. red and blue for the purple emote). If you fail, you have to fight an add. If you succeed, you're teleported up to a small platform. The platform will cast a debuff on you depending on which color it is. Sa'Dax has a stoneskin buff while on the platform. Target and kill the platform. Once you fall, you may have to pull Sa'Dax around a bit because the game seems to have trouble with the Z-axis in this fight.
Blackhand starts the fight by giving you an uncurable trauma effect that causes him to do more melee damage to you the further you are from him. He also has an ability called Pelican Dive that causes a group curable trauma.
During the fight, grimlings will appear near the ceiling and start throwing firebombs. Catching on fire causes an uncurable elemental DoT, but while on fire, you can touch the tapestries around the edges of the room and transfer the fire to them. This will also scare the grimling off the tapestry. It will join the fight as an add, but isn't very tough.