If you make a shield before opening the door, he'll drop little bombs on the floor that can roll right under your shield and kill you. The trick is to make a shield, then open the door and, when he drops a bomb, back up so that the door closes. The bomb bounces off the door and kills the guard. After the guard is thoroughly dead and there are no bombs on the floor, go through the door and super-blast the door behind the dead guard's shield. Then go right. Above you is a re-charger. You can use it but it doesn't seem to really matter because you never run out of gun energy after the first re-charger. But do it anyway because the animation is really nice. Now go right to the next area. This area overlooks a domed area with some green spheres hanging from the ceiling.
Look at the spheres and you'll see a tan dot reflected on them moving back and forth. This is a guard who you can hear pacing in the room below you. Crouch and wait patiently for the guard to stop pacing directly below the sphere, then fire, causing the sphere to fall on him. Do not fire until he has actually stopped beneath the sphere. Then go left to the staircase where the fleeing guard was and go down. Use the teleporter to get to the floor and head right until you reach some water. This water was the empty well whose wall you shot out earlier and which is now filled from the water in the reservoir you emptied. Jump into the water and swim down.
When you reach the tunnel at the bottom, swim left into the tunnel and keep swimming through the next room. Do not pause because you'll run out of air quickly if you dilly-dally. In the next room there is a shaft leading down and two shafts leading up. Swim up the leftmost shaft leading up. At the top of the shaft is an air pocket where you can catch your breath. After you dog paddle in the air pocket for a few moments, swim down again to the room with the shafts. Now swim down the shaft leading down. In the lower chamber, swim over to the ledge and climb out into the underground grotto. Do a standing jump to the right which just barely clears the floor jaws.
Then walk to the right and shoot the power line in the wall. Then go back to the left. I've always used a running jump to get back into the water but a standing jump might be alright. Once back in the water, swim up to the air pocket for more air, then swim down and back up the well to the surface. Then swim to the right side of the well and climb out. Walk to the right and you'll see the dead guard who the green sphere fell on. Continue walking to the next room where there's a shaft in the floor leading down.
Drop down through the hole in the floor and immediately use a super-blast to shoot out the down on your right. Since you managed to shoot out that power line in the grotto, the left door is jammed which slows down the guards since they have to super-blast it open. As soon as you have the right door blasted, start running to the right. There will be more doors but these will open for you without trouble. Don't stop to repel the shooting guards, just keep running. The doors close behind you as you run but the guards super-blast them open again. Above you, your friend crawls along a tunnel. When you reach the end of the tunnel, get beneath the panel in the ceiling, then turn and fight off the guards.
Keys für Revelation Online