Up next comes a major bit of exploration, but this time the boss battle is near the start rather than at the end. To start, return to the Reactor Core.
Locate the Yellow door on the upper level and blast it open.
Don't go in too far because you are immediately attacked by a sentry. Defeat it, go into the room a bit further, and defeat another which appears in the next doorway on the left. There is a cracked window made from Denzium here, so break it with a Power Bomb to reveal a portal, then go through.
Hive Portal Chamber (Dark side)
The dark, tougher version of an Ingsmasher is waiting for you in one of the alcoves on the far side. Be sure to get a scan because these don't appear often, then defeat it you would a regular Ingsmasher except use Light beams when possible. The Ingsmasher broke through the glass protecting its alcove giving you the chance to go inside, so use the portal there.
Transit Station (cont.)
In case you haven't guessed already, we're going to be doing a bit of portal hopping in this room. Follow the tunnel to the next alcove and use the portal there.
Hive Portal Chamber (cont.)
Follow the Spiderball track to a third alcove above the other two. Again, use the Light Portal.
Transit Station (cont.)
Follow another Spiderball track to cross over the main room and into a small room opposite the alcoves. Here you can collect a Power Bomb Expansion as your reward for completing the maze. Just use the Spiderball again to escape.
At this point you may want to go back to the Reactor Core for a quick save before going on. Then continue to the next area.
This is a large and complicated area. First defeat the quads here, then, before doing anything else, Spider back to where you came in and get a scan of the top of the large cylinder in the center. It's the boss for this room but you won't get a chance to scan it later. Drop down and scan the hologram next to the Yellow door here; the door leads back to Torvus and we'll be covering it later.
To the right of the Yellow door is a Spider Ball track with hammers, rolling pins and other implements of destruction. Time your way past the various obstacles — there are too many to go into much detail — to reach a Missile Expansion.
Now switch to the Echo Visor and locate the emitters locking a door on one side. Shoot all three to open the door and reveal a portal, then go through. You may notice that the drone in the cylinder starts to get excited.
Staging Area (Dark Side)
There are two Hunter Ings here and the battle can be awkward because there are no beacons or crystals to help keep them in check. When they're gone, switch to the Echo Visor again and locate another set of emitters to shoot. Get all four, then scan the panel that's revealed. A hole opens in the floor allowing you to drop down below the central cylinder where another portal is waiting. Before using it though, wait in the safe zone until your health is completely restored. There is another exit you can reach at this point but it's a dead end for now.
Main Research (cont.)
Now it's time to confront the boss here; there's no actual boss bar with this but it has boss music and it can be a tough battle, especially on your first playthrough. Start by Spidering up the track.
When the battle is over, Spider up to the top, then follow the tunnel and drop into a hole. Follow the track down to reach a high ledge. There is no other reward at this point, the whole battle was just to reach this ledge. Note that if you fall off the ledge instead of doing the obvious thing and going through the door here, you can get back again by re-entering through the portal and following the Spider Ball track inside the cylinder again, this time the drone wont' be there.
Central Area Transport West
An Orb Cannon is here but it's sealed in a cylinder and you must clear the sonic lock. So switch to the Echo Visor and clear the emitters. Once this is done, roll into the cannon to be shot repeatedly until you reach the top. There is still an expansion to get here though, so drop down a level and look for the morph ball track in the wall. You can follow the track in two directions and from there there are multiple paths down a kind of maze back to the start. You need to follow the correct path to get the expansion, which shouldn't be hard to find. If you don't want to work it out yourself, use the left path at the top and then go right whenever you have a choice. Use the Orb Cannon to get back up to the top.
This is another large room and the first thing you may notice is that there's no bottom to it. There's some platforming to do here but remember that if you fall you only take 10 points of damage and are placed back a short way. First hop onto one of the floating platforms and clear the Rezbits that are lurking around. Look for a White door and jump to the ledge in front of it. We'll be going in there soon, but first scan the hologram there, then jump to the White door and to a ledge on the right where a Spider Ball track start. Continue left on the track where there is a branch going up and follow it to then where you can drop off to a platform with an Orb Cannon.. Note that if you continue right at the start you'll be take to a door which, on the map at least, looks like it leads back to Sanctuary Temple; it's really a dead end though.
Use the cannon and grab on to another track before you fall. This is a long and tricky track to follow, and watch especially for spots where you need to bomb jump before the track carries you to a barrier which knocks you off. Fortunately there are red markers above and below the track at the exact spots you need to drop a bomb in order to reach the next section. Eventually you come to a fork where you need to take the left path. Continue on and, perhaps after a few tries, you'll find yourself in a tunnel. At one point in the tunnel you are given the choice between going forward (i.e. the direction the camera is facing) and going right; continue forward. There is a short tunnel with a Beam Ammo Expansion at the end. Go back and follow the tunnel right to be dropped down near where you started.
Go back to the White door and this time go through.
Watch Station Access
Drop off the ledge and grab the Energy Tank. Now scan the panel nearby to lower Grapple points in the long bottomless corridor next to it. This creates a shortcut back to Main Gyro Chamber; you may have noticed the White door there before but it's no longer a dead now. As long as you have the shortcut, you might want to use it to get in a quick save before going on. Go back.
Watch Station (cont.)
Get to the Orb Cannon again and follow the Spider Ball track again, but this time take the right path at the fork. This takes you to a Bomb Slot which opens the gate blocking access to a portal, so go on through. There is another door to the left of the portal which we haven't mentioned yet, but it's a dead end at the moment.
Aerial Training Site
There more to do here later in the game, but for now you can only go through the door to the left of the portal, the one that was a dead in light side.
You have a wide chasm to cross, but this version of the room, unlike the other version, has Grapple Points you can swing from. Clear the Preeds out of the way first so they don't interfere with you while you're getting across. When you land, hop down to the platform on the left, then back under to a portal under the ledge.
There is nothing to do here but get the ledge above and go on.
The goal is now in sight, but it's caged in a Luminoth vault. Drop down behind the vault to find a Bomb Slot, but activating it does nothing for now. You'd think that by now you've earned the upgrade, but no, you have yet another puzzle to solve.
From the bomb slot, drop down a bit more and scan the panel on the other side of the vault. This lowers the bridge here so that you can reach a portal under the door you came in through. Note that it also cuts off your way back until you collect the upgrade for this area.
Vault Attack Portal (Dark side)
The bridge is still above you in this version, and there is a series of Grapple Hooks for you to use. Some speed is needed though because Dark War Wasps attack when you start. You can destroy some of the hives beforehand if you scan the bridge to find them, but you won't be able to get all of them.
You might want to stay in the safe zone a bit to restore energy, then use the portal there.
You're now on a ledge behind the vault and there are series of platforms to the left and right. These lead to a total of four small arches and you must get to the platform under each arch and use the Spinner there to turn each arch around to face the vault. The tricky part, aside from making what seem like impossibly long jumps, is that the platforms are guarded by Rezbits that wake up when you get close. These can easily knock you off the platform you're on, which means having to start again from a previous platform. The Rezbits are a bit more challenging than usual here because there is no cover and little room to dodge.
When all four arches are facing the right way, use the portal to return to the Dark side.
Vault Attack Portal (Dark side)
Basically the same as before but in the opposite direction. Use the portal yet again.
Use the Bomb Slot now and it will fire lasers at the four arches and open the vault. Pick up your reward for all this, the Screw Attack.
The Screw Attack isn't really an attack but an extended double jump. Press B twice as for the space jump, but keep on pressing to fly through the air in somersault. You can now get back to Grand Abyss by using screw attack, but you may want to practice a few times going back and forth here while you still have the bridge as a safety net. You can then use Screw Attack again to cross the Grand Abyss without Grapple Hooks, in fact Grapple Hooks are pretty much redundant now.
Expansions (Ing Hive)
There are quite a few expansions to get at this point; we'll start in Sanctuary Temple, then head for Torvus opening up a shortcut on the way, and wrap up in Agon.
Aerial Training Site
Return to Watch Station and use the portal there to get to Aerial Training Site. Above and to either side of the portal are rectangles with a mottled pattern. Get a scan of them to learn they are a device you can use the Screw Attack. The idea is to Space jump toward the lower of the two panels, then press B again to jump off the panel like a Mario style wall-kick, then kick off from the opposite panel just as you touch it, and so on until you reach the top. This is tricky to master; for one thing the timing can be finicky and for another the camera changes from first person to side view which can be disconcerting. But there are several places where you need this move to reach helpful expansions and you'll also need it to reach one of the final bosses to complete the game. This is a relatively easy one to train on, so give it a try and two bounces later you should land on a high ledge with a Missile Expansion.
You may spot a key here and we'll get that next, but it will mean taking a detour.
Take the portal again and continue back to Main Research, then use the portal here to reach the Staging area. There is now a ledge around the central cylinder at jumping height, so jump up and locate the ledge to one side. Jump again to reach a door and go in.
Central Hive West Transport
There are two more Wall Jump Surfaces here but this time they'll put your skills to the test. Wall Jump to the top to land at a new door.
Aerial Training Site (cont.)
You come out in a small cage containing a key. Activate the panel here to remove the cage, then you can Screw Attack back to the portal.
Expansions (Sanctuary Fortress)
Head back to Main Research and blast open the Yellow door on the lower level.
Torvus Transport Access
This very similar to the Power Junction and there are more Octopedes.
Transport to Torvus Bog
Activate the lift and take it.
Expansions (Torvus Bog)
Transport to Sanctuary Fortress
Go through the door to the next area.
Fortress Transport Access
There are two sets of revolving platforms above some water here. Going from the Fortress to Torvus you can just jump in the water and climb the ramp out, with only a Blogg to slow you down. But coming the other way you must negotiate the platforms. Blast open the Yellow door at the far end, assuming you didn't clear it already, to finish the shortcut to the Training Chamber.
Undertemple (Dark side)
There's another expansion we can get here as long as we're in the area. Get to the Hydrodynamo Shaft and take the portal to Undertemple Access as when you got the key. then go down to the Undertemple where you fought the Power Bomb Guardian. Go to the side room with the portal and notice there are Wall Jump surfaces here. Wall Jump to the top and grab a Missile Expansion. You can now drop down to the portal.
Get back to the surface of Torvus and go to Meditation Vista. You may have noticed earlier a platform floating off the cliff, and now it's finally time to see where it leads. Use the Screw Attack to jump to the platform; it's small and moving so it may take a few tries, but remember that the consequences of falling are pretty minimal. It's probably best to start from the left side of the portal. When you do land on the platform it takes you to an Energy Tank. Getting back to the ledge should be much easier than landing on the platform.
The shortcut to Agon is just across Torvus Temple, and that happens to be where we're going next.
Expansions (Agon Wastes)
Get to the Mining Plaza and notice the three large disks above the central platform. These are actually lenses that are controlled by sonic locks. So switch to the Echo Visor and disable the emitters in the usual way. The Sand Bats may interfere with your targeting some, but you can shoot them first to get them out of the way. When the lenses are in place they open a gate with an Energy Tank behind it, but you won't be able to reach the tank without the Screw Attack. Actually landing in the little alcove where the tank is hidden may take a few tries.
Get to the Sand Canyon; if you're coming from Agon Temple you may want to use the Orb Cannon to get to the side closer to the ventilation area because it's a bit higher. Use the Screw Attack to get to the platform in the middle of the area, then notice that the base of the structure there is made from Denzium, so blast it with a Power Bomb to knock it down. Grab the Power Bomb Expansion there and use the Screw Attack to get back to the Agon Temple side since it's lower.
You should now be fairly close to the shortcut back to Sanctuary Temple which is the next stop.