Dead Space 3 walkthrough, Part Thirty-Three: What Lies Below
Danik's stolen the stupid Codex! What's worse, he's headed into the depths of the planet via the Research Silo to turn off the Machine, which is now, apparently, a very bad thing to do! The situation gets more and more complex… but it's obvious, at least, what Isaac has to do: put a bullet in Danik's brain. Chase him down the Research Silo!
Use the winches here to rappel down the side after him. Don't be too concerned with getting close - you'll just get shot at and not catch up. Watch out more for the Necromorphs that scrabble along the walls at you. Be ready at the next ledge, as well, because more of the things will be waiting. Go down the elevator.
In the next area you'll have a few moments to take potshots at the elevator before it disappears again. Once it's gone, head down the walkway. You'll find a Heavy S.C.A.F. Frame and more winches. Take the plunge. As you head down you'll be targeted by Danik's men on walkways below you, though they all have explosives next to them. Target the explosives for an easy trap. Keep your eyes on the right side on your way down for a Rail Accelerator you can snag with Kinesis. Duck immediately when you get to the bottom and trade shots with the soldiers on the opposite platform.
Through the next door you'll find a Safety Guard on a shelf. Get through security here (these ones get especially confusing, so try to keep the left stick to the left and the right to the right) and you'll find a room with a recording, a Bench, a Suit Kiosk and some items, notably an Upgrade Circuit in the second half of the room. Prep yourself adequately, then go through the next door. You'll find possessing Necromorphs taking over the bodies of the soldiers you killed. Aim for the heads and look for little scuttling shapes on the ground.
Another winch! As soon as you begin to descend you'll come under fire. Let the elevator get down far enough that they're not shooting before you proceed, as you'll have more pressing matters to worry about as you descend: wall-crawling Necromorphs that explode on contact. Back up and blow them away before they can reach you.
Keep descending. Near the bottom the elevator will come under attack by a large Necromorph whose head looks an awful lot like Rosetta's. Hm. It will jump on the wall to attack you; use Stasis to keep it back and fire away at its legs. Eventually it will detach and fall - though it won't be dead, as it's now apparently attacking the soldiers on the platform below. Help the soldiers by aiming at the creature, then take out the soldiers. After all is done, check the lower walkway for a Javelin Gun blueprint, a Heavy Standing Frame and various items. Go through the nearby door.
Beyond is a ventilation shaft and more winches. Go down and one of the huge Rosetta-esque beasts will come up towards you. Stasis it and aim at one leg to send it flying down the shaft. Further down are more exploding Necromorph mites, and beyond that, a combination of big and small. Stasis on the latter encounter is recommended. At the bottom you'll find a fan; use Stasis to get past it, then pound X or A to get free of your tow cable once beyond. You'll get dumped in the snow below.
Danik will freak out on the nearby elevator and head off. Nope, you don't get to kill him yet. Use the generator in this small area to get the Bench working, look around for items (notably an Alien Artifact hidden behind a big cube of ice) and prepare to enter the Alien Ruins.