Ing Hive
It's time to face the final boss for Sanctuary Fortress. As you might expect, it will be the toughest in the game so far
Hive Dynamo Works
Get to the Hive Dynamo Works; you may remember passing through here on the way to the Spider Guardian on your first entry into Sanctuary Fortress, but there's no reason for you to have come back since. There is a White door which we will finally explore.
Hive Dynamo Access
Defeat the Ing here and switch to the Echo Visor since there is a sonic lock here. Disable the emitters as usual to open the gate and continue to the next area.
Hive Gyro Chamber
There are three exits here in addition to the White door you entered through. But there's not too much need to guess where they lead since the map of the Light side tells will give you a good idea. The Blue door in the room above the White one leads to the Sanctuary Temple on the Light side, so it's a safe bet that it will lead to the boss on the Dark side and so we'll save it for last. The Red door opposite the White one is obviously going to be a Save Station so let's save that for next to last. The only two things left are the key, which the hint system may be pointing to by now, and the door above the Red one. We'll start with the key.
Look through the window to see a large sphere with platforms circling it. It's really a giant Spider Ball Track, so hop to one of the platforms nest to the sphere, switch to Morph Ball, and grab on. The sphere is guarded by Darkling Tentacles though, so either avoid them or drop bombs to make them retract. If you fall, which is likely if you get hit by a tentacle, just climb up the Spider track under the sphere to start over; there's even a small safe zone down there just in case. Climb the small track at the top, then Boost jump to the ring around it, and Boost jump again to collect the final key.
Now start hopping platforms to reach the room above the Red door; if you get disoriented it's the one without the two columns of light.
Hive Gyro Access
There are more Ing here but otherwise just continue to the next area.
Hive Ammo Station
Refill your ammo here for the upcoming boss and go back.
Hive Gyro Chamber (cont.)
Drop to one of the lower platforms and hop into the room with the Red door.
Hive Save Station 2
It's a good idea to save because, in case we didn't mention it, there's a boss. Go back.
Hive Gyro Chamber (cont.)
This time jump to the room with the two columns of light and continue to the next area.
Hive Temple Access
Step forward to automatically place the keys in place. There is a light beacon in case you want to do some last minute healing.
Hive Temple
Step into the lift and forward for a cut scene where a giant mechanoid is possessed by and Ing, perhaps several, and comes to life. You may recognize it somewhat since the pieces of something similar where scattered around Sanctuary Temple. But here the machine is fully assembled and functioning perfectly.
The monster leaves the Annihilator Beam behind. (It's very likely that it was using it against you a minute ago.) Pick it up and the robot disintegrates; in its place a platform rises out of the floor. Spider up the sides of the platform to where you'll be in Screw Attack range of the exits.