The panel to open the gate before you is right here (#131), but for now you lack the necessary code. Enter the tunnel, fighting off creatures and tentacles. At the end of the road you'll see a screen (#132). Wait for Talon and when he's around you'll understand the code - it's 0634.
Get back to the panel. When Talon sits on it, enter the right combination. The gate will open, so go through it and reach the platform with a school bus near it. Spirit walk through the glowing path to get near the wreckage. Use the button (#134) to open the next door and get back to your body. Approach the gate - the lights will go out and the bus will be filled with a strange glow.
You'll be attacked by children ghosts again. As always, you have to use a gun against them. Then all of them are back to the dead, approach the gate and crawl to the next room.
Go forth, eliminating all the creatures that come into your way. Don't stop until you're in a room with two wall walks in it. One of them is deactivated for now. Push the button (#135) and go up. The room will be filled with enemies, who will turn off the machinery. Kill them all and use the button again.
As one of the walks is damaged, use the second one (#136). When you're in the next room, take care of the Fodders and push the cocoon towards the tunnel blocked by a green ooze (#137). Shoot it to open up the way.
You'll find a chopped off hand (#138) which belonged to one of the hunters. From now on you'll be able to open all gates that require you to put your hands on a panel. There's a room nearby in which you'll fight the first really challenging opponent.
Wait patiently until Centurion deals with the civil, and your cage will be crashed. The beast (#139) is completely resistant to your attack, so don't even try to shoot it - waste of ammo. Just let him kill you. After coming back to life, you'll reappear in the same room, but this time he won't know you're there.
Wait for the creature to destroy the energy barriers that were blocking the way to two small rooms ahead. Run to one of them (#140) and hide behind a corner as fast as you can. When Centurion approaches and tries to shoot you, use the switch to turn the force field back on (#141). That'll chop off one of its hands, and you'll get a powerful destruction device (#142).
The grenade launcher, combined with the machine gun, can finally damage the beast. Shoot all you've got at him until he drops dead. Don't pay too much attention to your health - you're immortal after all.
When Centurion is dead at last, a portal will appear (#143) and a hunter will jump out of it. Kill it and use the portal to get to another part of the complex. After a short walk you'll see another room with a web of wall walks all around it. Use them (#144) to avoid the force fields and gather all the ammunition.
Kill the approaching enemies and find the closed door (#145). Use the hunter's hand on the panel to open it. You'll reach a room with a huge, blue portal in it (#146). Push the button and wait for the machinery to stop, then use the portal. Enisi will speak to you again, summoning you to the magical real of the Indians.