The round room you are in has a Tentacle hanging from the ceiling. Get it and avoid the fire from the two Krall beyond the barred hallway. If you can kill them from here it will make things easier for you later. Enter the open hallway and you’ll come to a watery chamber with three Krall standing guard. Use the hallway to take them on individually and then enter the chamber.
Climb the beams and shoot all the barrels to find some goodies and push the lever to raise the bars in the other room, then shoot the barrels in the water below. There are plenty of Devil Fish so beware as you dive in to collect some ammo on the bottom. Return to the other room and enter the newly open passage.
Use your Eightball Gun to lob some grenades up onto the landing on your left to killer the Lesser Brute waiting there. Walk toward the alcove on your right and a lift will lower. At the top two more Krall are waiting. Turn the capstan to open the main doors below, and quickly get down there and through them before they close.
Turn left once inside and follow the hallway around to the left. Walk up the slopped support along the right-hand wall and get the AutoMag Clips on the balcony. Jump down and walk up the stairs on the right to reach a landing with a RazorJack on it. Below the landing there’s a chamber with a Krall inside, kill it and get the Flak Shells from the barrels inside then push a lever to open the inner doors. This also opens another passage that will allow you to get inside even if the inner doors close.
Enter the inner castle. The open room on your right is unoccupied but contains more supplies. Turn right as you leave this room and take on the two Skaarj around the corner. Collect the Eightballs in the crates on your right, then head down the corridor and up the stairs at the end.
The chamber at the top of the stairs is a trap. There’s a Titan inside and the exit will be bared as soon as you enter. However Krall will swarm inside and attack both you and the Titan. Push the loose block on the back side of the central pillar to open a secret door. You can leave the room and hide up the stairs but you’ll have to deal with a Skaarj. Kill the Skaarj and walk out onto a platform over the room below. Lob grenades onto the Titan below and let it slam you into the air. You want it to toss you high enough so you can fall into the cistern in the centre of the platform. Once in swim down inside to collect the Stinger and Tarydium Sludge, then swim back out and finish off the Titan. Do NOT go back into the room below.
You need to make a tricky jump to get out of here to small landing above the barred door. You need to line up with it and start your jump mid-platform, otherwise the sloped ceiling will knock you down to the Krall below. Once you make the jump, push the button to open the gate below and escape the chamber.
A new hallway is now open on your left. A Skaarj is waiting in the shadows, get past it and push the lever. Turn around and enter either door on the right and climb the stairs. Fight the enemy upstairs and get the Eightballs from the ledge. The levers and weights at the other end of the chamber serve to lower a lift near the ledge with the Eightballs on it. Ride the lift up and kill the Skaarj lurking above. Walk along the ledge in this upper chamber and push the button before jumping onto the platform below to get the Super Health Pack. There’s a secret panel under the water with an Invisibility power-up inside. Get it and fight off the Devil Fish to reach the lever on the bottom of the pool. It opens the doors out of this area, so swim up and exit through either door.
Go back downstairs and enter the room across from the stairs, where you’ll see that the bars over the opening inside are gone. Walk into the new area and empty the barrels of their Tarydium Shards before taking the stairs.
When you reach the bottom, bars will block the stairs behind you and Krall will attack from the darkened room. Run to your left and enter the alcove to ride the lift inside up. Kill the Skaarj that drops in on you, then walk along the landing ahead to reach the lever and open the bars blocking the room. Collect the Flak Cannon and Super Health Pack atop the crates below you as you exit. A horde of Krall will attack. Head for the pool and dive in. Kill the Devil Fish you encounter and swim through the gap in the bars toward the underwater shaft with no grate on it. Get some air and follow the shaft to a small chamber with Tentacles hanging from the ceiling.
Kill them and get the Assault Vest and goodies and push the lever. Swim back up and through the bars into the area outside. Go into the hallway and leave this part of the castle through the passage and turn left, The gate is now open giving you access to the rest of the castle so enter and look right to avoid a Behemoth attack.
Walk down the stairs and push the lever to open the doors across the hall. Inside many Krall and a Behemoth are waiting, lure them into the hallway to deal with them individually, if you can make them follow you far enough you may be able to run back into the room and push the lever to shut them in the hallway. However you choose to do it, clear the room and turn the wheel to lower twin lifts to the upper level. Upstairs you’ll find a stairway behind one of the lifts that leads to a roomful of crucified Nali with Nali Healing Fruit beneath them.
Head the other way from the lift and you’ll find some Eightballs and a passage that leads to a room with a Krall, once you’ve killed one others will drop from the ceiling one-by-one. Krall perform very well as a team, so you don’t want to face more than one of them in this room. Stay on top by listening for their fall and charging with Stinger, MiniGun or Flak Cannon blazing. When they are all dead the gate will open.
In the next area take on the Behemoth and Lesser Brutes and push a lever to bring a lift down. Ride it up and get the goodies then push the lever, this will open a panel behind the lift. Follow the passage behind it and enter the Nali Castle.