1. The walls here seem irregular but actually the path is linear. Nomad notices a current pushing him back and decides to move against it. So just keep going against the current, brushing past the particles flying against you.
2. If you move quickly you may get a glimpse of the creature that smashed the grate. It moves fast and disappears. You are not alone down here.
3. Keep going against the current. When you see a large circular opening below, go through it.
4. The tunnel continues. Soon you'll see a vent emitting a strong jet of steam-like gas ahead. Move close to it.
5. With a roar, an alien creature will dash at you and hit you.
6. The Crysis gaming community refers to these guys as "Naked Alien", as they don't have an exoskeleton. They have glowing translucent bodies and move around very fast like fish underwater.
7. Their charging melee attack is very powerful. A straight hit depletes your armor completely and causes partial health damage in Normal difficulty.
8. Once the Alien retreats, closing the vent behind him, move to the opening on the right side.
9. The current is so strong here that you can't move forward. Nomad comments that these machines must be generating the current so he has to knock out the power.
10. Shoot the capsule-shaped machine just ahead that has a stream of energy running through it. That will stop the current. Now you can keep going.
11. Down below there is a strange fluffy tube that seems to carry power. Follow it to the other end.
12. At the other end the tunnel seems to curve up. Go up and go past the circular opening.
13. When you emerge from the hole, you'll see three paths straight ahead. All three of them will just loop you back to the original position. Instead, move to the circular hole above, marked by the arrow.
14. As you approach the hole, a small cutscene starts.
15. Out of the blue, an Alien pokes his face at you and emits a good long roar. Gosh; these things are ugly. The Alien pushes you back to the cave leaving you stunned.
16. The Alien will be moving around the loops of the cave and charging at you to make its melee attack. Get ready to fire. When charging at you, these guys will emit a screeching roar so when you hear that, step aside and look around to locate them.
17. The best chance to shoot at them is when they charge at you. They don't have much health so they'll go down with a couple of well-placed shots with the shotgun or about 10 bullets with a rifle.
18. Note that you can grab the Aliens when they come really close to you, just like you did with KPA soldiers, although this is very difficult due to their high speed. Grab an Alien and throw it away to make an instant kill.
19. After killing the Alien, get through the hole. You'll reach a narrow tunnel. The pentagonal door at the end will not open, so go through the grate to the left.
20. You'll reach a chamber with something that looks like a giant exoskeleton. Nothing of importance here. Just go ahead and turn right.
21. From the chamber you will pass through a series of arches. There is an oval-shaped opening ahead. Move through it.
22. The opening takes you to another large chamber with a lot of eye-catching objects. When you come here, Nomad will ask "What is this place". This is an alien generator room.
23. Two display panels just ahead show diagrams of the Aliens. Move past them and look under.
24. You'll see capsule-shaped generators containing swirling streams of energy. There are several Aliens also in the chamber. They won't attack you until you open fire.
25. On both sides of the chamber you can see several Aliens in some kind of stasis.
26. Your objective is to destroy all five of the power capsules. Shoot the glass to destroy them.
27. The shooting will, of course, alert the Aliens and they will start attacking you. As said earlier, it's easiest to kill them when they are charging at you.
28. One by one, more of them will wake up from stasis and join the fight. Destroy all generators fast.
29. The Aliens prefer to attack you from the back or sides. When charging at you, these guys will produce a distinctive, high-pitched roar. When you hear this, turn around and move aside to dodge the attack.
30. Note that if you do not use the flash light attachment, the Aliens will not be able to detect you while you are in 'cloak mode'. Use this trick to sneak away.
31. When all the generators are destroyed, a pentagonal door will open at the bottom. It's easy to spot because of the lights lining the edges. Escape through the door.
32. You will reach a rock cave with ice crystals on the walls. Although the walls are irregular, the path is linear. Keep going.
33. At the other end, there is another grate. Break it and enter.
34. The grate opens to a tunnel. Turn left and proceed.
35. The tunnel curves up, leading to a hole. Go through it.
36. In the next chamber, there are two deposits of objects from the outside. Apparently the Aliens have been gathering objects from the outside. You will find guns and ammo (not the magazine!) among other stuff.
37. Stock up on weapons and ammo from the deposits. You'll find FY71 rifle and incendiary ammo for the same, which is highly recommended.
38. One of the deposits holds a minigun. But sadly the fast-moving Aliens are good at evading fire and the minigun will run out of ammo before you can kill many of them. So pick up the minigun only if you want to scare the Aliens.
39. At the far end of this chamber there is a hexagonal window above a couple of display panels. Look through the window to see some heavy alien production machines at work.
40. Take the tunnel to the left to exit this chamber. The bioelectrical cable leads to the tunnel so it's easy to spot.
41. The tunnel will take you to a small room with several display panels and a lone alien working at the panels. Switch to cloak mode before moving in if you want to sneak up on this guy.
42. Sneak up from behind and grab then throw it away to score an easy kill. Or just put a shotgun round through its back.
43. From here, move to the passage which will be to the right if you look from the tunnel you came through. You'll find yourself at the hall with heavy machines that you had watched through the hexagonal window.
44. This hall is separated by three energy shields that act as gateways. The shields turn on and off in a timed sequence as the machinery operates. As Nomad suggests, you have to step in as each shield opens. The sequence is fairly simple anyway.
45. Several Aliens will be on to you, but they can't pass through the shields either.
46. The Aliens mostly resort to the crawlspace at the bottom of the hall so keep your eyes on the ground. FY71 incendiary ammo seems to work best for this battle.
47. Note that you can sneak through instead of engaging the enemy by using 'cloak mode'. Make sure you don't use the flashlight attachment.
48. Some of the Aliens here will be carrying a weapon as seen in the picture that fires a stream of ice crystals. The ice crystals damage you just as any automatic rifle fire does.
49. Once you are past all the shields, you can see the other end of the hall that looks like a demonic face. The tunnel to the right just pushes you back while the one on the left will suck you in. Take the left one.
50. You will be taken in a long, ultra speed journey through various parts of the alien structure. Just sit back and try to get a glimpse of the areas that you pass through.