Dead Space 3 walkthrough, Part Thirty-Seven: Blood Moon
Isaac has the path to the Machine open to him. Only one thing stands in his way now: Danik and his Unitologists. Unfortunately, they appear to have captured Ellie to use as leverage against Isaac. No good, this, no good at all.
Go through the path to get to the Heart of the Machine. In the first room you'll find a pitched battle between Danik's men and a Rosetta Necromorph. Help the Necromorph while they're distracted. After they're dead a slew of exploding crawlers will appear; be ready for them. In the second half of the room you'll face another squad of Unitologists. Watch out for grenades.
The next room features a puzzle, but you have Unitologists to take out first. Run along the walkways to your left, grabbing one of the movable barriers here to give yourself some cover. Blast away at the Unitologists hiding in the far doorway. Once they're down, turn back to the right to counter the soldiers running along the platforms. The first will be suicidal with a grenade; the rest have guns and lob grenades. Keep low to avoid getting hit, and don’t be afraid to throw the barriers at them if they're close enough. Once they're all dead, place the glowing green boxes along the edges of the Machine in the red receptacles near the middle to open another door.
Inside you'll find the final message from Dr. Serrano (and, presumably, his body - poor guy) and some climbing gear. Activate the winches and begin the ascent up the middle of the machine. There are two hazards to contend with. The first are three lines of vents that activate periodically and will do damage. Rappel around to avoid these. The second are two giant gears that will kill you if you get too close. Wait for a gap in the gears and use Stasis to crawl through when the vents are inactivate. Not difficult, just a bit tricky.
You'll find Carver waiting at the top. Check around for containers, then approach the forbidding-looking Codex slot. Danik will pop in with Ellie, and, long story short, he'll shove it in the Machine. Things will go bad, you'll hit the final chapter, and the world will begin to ascend into a very bad place.
The first part of this next section is all running. Don't stop or slow down for even a second. You should only pause when you begin to see containers, as Necromorphs will start to appear. Ignore the small fries and concentrate on the big tentacles that will eventually be blocking your path. Take out both of them to continue onward - though don't neglect to look back, down a lower path, to find an Alien Artifact. Beyond the ruins of the tentacles is a flying segment; blast right past the Necromorph blobs along the way.
You'll land in a snowy area next. Run ahead until you come to two jittery Necromorphs. Kill them, as they'll make blowing up the tentacle ahead way too difficult otherwise. Blast the tentacle and keep running. There are more Necromorphs and more confusing running sections ahead, and your best bet generally is to just plow through. Unless the Necromorphs are especially fast, don't pause to kill them.
Soon you'll find the game's last Bench and last Suit Kiosk, and despite how it looks outside you have some time to prep here. Med Packs are a must past this point, and ammo certainly doesn't hurt. Check the door here and you'll be blasted out into empty space; enjoy the cinematic flight through all manner of debris, then prepare for your battle against Blood Moon, the final boss.
A massive, multi-eyed creature, Blood Moon hangs in the background throughout this fight. It will begin by releasing several rocks that will further release Necromorphs to take you on. Stand on the TK charging plate in the center of the island you're on and you can use the Necromorph's own limbs against them, preserving your ammo for close encounters you can't avoid. Once the Necromorphs are out of the way, grab the Markers hovering nearby and launch them at Blood Moon's three eyes.
Once you hit one of the eyes Blood Moon will try to eat the platform you're on. Blow its tentacles off, get rid of the subsequent Necromorphs that appear, and wait for another chance to launch a Marker. After the next one Blood Moon will try to eat you once more, and release three more waves of Necromorphs, before bringing its final eye around. Target it one last time. Once that's done, latch onto what's in its belly and heave it out to spark the ending sequence.
Congrats! You've beaten Dead Space 3! Enjoy the ending, and when it ends you'll find a bunch of new stuff unlocked, depending on your difficulty level.