Kill the fiend ahead, then turn right at the top of the slope and kill the scrag. Search and the destroy the two knights hiding in the shadows to the left of the entrance. Two more knights appear from the doorway with the yellow sun symbol. Grab the grenade laucher in that room, the pool here counts as a secret area, it heals you if you step into it. Exit the room and shoot the sun symbol, a wall drops behind you containing a fiend and a pentagram of protection. Deal with it, then renter the room, Go around to the next area and battle another pair of knights, the room after, with the staircase, also has a pair of knights hiding in the shadows either side of the entrance. Run up the stairs and go down the hall and be prepared to deal with the two fiends that pounce. When you are able, step onto the lift in the passageway that's just above the stairs, under which you can see the red armour, As the lift rises step off of it and quickly walk into the area under it, kill the knight and enter the secret area containing the armour. Step on the floor button to open an exit in the stairs. Walk over the stairs and enter a room with a fiend. Work your way to the water, kill the scrag, if you jump in the water you will have to deal with the rotfish, so throw a grenade in first. Jump in the water, and swim to the plank on the left, jump onto the ledge for the super nail gun, then turn around and kill the fiend as the wall behind raises. Grab the box of 100 health bonus. Then go for the scrags. Now return to the lift you stepped off earlier. Ride it up and deal with the death knight, work your way around the corridor, dealing with several death knights and fiends. Pick up the 100% armour. When you return to the lift, turn right and find the walkway around the corner, kill the fiends and scrags, and continue weaving through the corridor until the walls drop revealing knights. Kill them then get on the left wall and ride it up like a lift, you will enter a secret area, grab the quad damage and jump through the portal. Walk up the stairs ahead, press the button and grab the ring of shaddows. Head for the moving plank at the other end of the water. When the plank is fully extended, jump over to land. Get the pentagram of protection, and the silver key, throw a grenade under the portal and step on to it, jump as it explodes and you should go through the portal and come face to face in a secret area with a shambler. Run into the next room, through the silver key door and then head through the exit.