Alright, last phase before the big boss throw down. You start the mission with Virgil telling you that you have to unlock the back up systems. Head down the hall closest to the exit on the right hand side. Double jump/angel boost over the gap, then at the end of the hall use demon pull to kickstart the generator.
A butcher will rise from the ground with a handful of stygian. You can knock the stygian into the generator to do some extra damage to them. After they are finished, take down the butcher. Now, return back to the main room and don’t forget the double jump/angel boost.
Run straight across into the other hall closest to the exit. In here, you will descend the hall and follow the ledge on your far right. Now, double jump/demon boost onto the platform in the center, then do it again to reach the far side ledge. Once safely across, follow the ledge down and into the next room. Continue around the ledge until you reach the generator in the center. Remember, if you get too close to the generator while it is running it will damage you.
Once the generator is started, a drekavac and a couple pathos will attack you. Take out the pathos first, but if you can lure the drekavac into the timed mines the pathos throw at you it wouldn’t hurt. After the pathos are gone, take out the few stygian that appear. Now you are clear to handle the drekavac.
When the room is clear, return back up the ledge. Double jump/angel boost twice to get on to, then from, the center platform. While exiting this chamber. demon shards will pop up, so be ready to shoot them down.
Now, head down the right side to the hallway closest to the entrance on your right. Continue down the hall and double jump/angel boost to the platform far below to your right. Double jump/angel boost to the center platform and start the generator with demon pull.
A ghost and blood rage will attack you. Handle the blood rage first, by pulling him toward you with the demon pull. If you keep him isolated, the ghost rage will hardly pay attention. Then, angel lift to the ghost rage and use the shredder move to keep him airborne.
After you finish them, double jump/angel boost off of the central platform and return to the previous room. Two demon shards will attack you while leaving, so shoot them down while backpedaling. Here, double jump/angel boost to the far platform. Now, angel lift yourself to the highest platform and return to the main room.
One last hallway to go. You can double jump the platforms in this hallway, they shouldn’t be much trouble. On the other side, take a left. Now go right and double jump to the first platform. Double jump again to the next one and use demon pull to start the generator.
A handful of stygian and a witch will be your challenge here, with a couple pathos popping up later. Use Aquila on the witch and take her out first, again using demon pull to isolate her. The rest should be easy from there. Double jump to the platform, double jump off of it and exit this room. Be careful in this hallway as there are a bunch of demon shards that like to show up when you are about to jump from platform to platform. Blast these shards away and return to the main room.
Now, Virgil will instruct you to match the markers on the floor with the ones on the pillars. Use the red markers in the center to turn the symbols clockwise between the four interacting gears. After you match up the symbols the mission will be over.
Article from Gamersyndrome.com