Reservoir
Step into the pool and head along the bottom to the left, underneath the path to Grasstown. You should reach another door, leading to the Chimney.
Chimney
Make your way up the Chimney, taking out bats and critters as you climb. You'll reach another door leading forward.
There will be a Teleporter Room here, with an available data card. You can return to Sue at any time to make this teleporter accessible.
Aqueduct
It's difficult to properly write a guide in regards to a jumping puzzle. Head to the left and follow the water current. It'll zig-zag back to the right on the second floor, and to the left again on the third. As you climb each floor, failing to make a jump will drop you back to the previous one, and the camera may have trouble keeping up with you if you're turned around.
In the second area is a centrepiece that redirects where the water is going. Use the console at the bottom to redirect it to the left, then use the console on the left to redirect it to the top. Follow the current up and carefully follow it to the upper area. There's a save room you can enter if you jump at the right moment.
After this save room, there's another section similar to the first one, split into three floors. You'll have to time both when you jump and the length of your jumps to navigate this section without getting hurt.
The final segment is a small maze. Keep an eye on where each current is headed, and pick whichever hole you think will carry you to the next part. If you fall to the bottom, be sure to quickly recover by jumping near the end, or the current will pull you back down to the first area.
When you finally reach the end...
BOSS: Alpha
Alpha will pop up out of the ground, open its jaws, and throw a bunch of rocks into the air before burrowing back into the ground. The indestructible rocks will vanish when they come in contact with the floor. Alpha is only vulnerable to damage when its jaws are open.
After enough damage, Alpha will stop burrowing and instead jump around repeatedly, spewing rocks after each jump. During this phase of the fight, Alpha will be vulnerable, even while its jaws are closed.
The strategy for this fight:
When Alpha is defeated, head to the door on the right.
Speleothem
The first half of the map is a straight path to the bottom of the map. Keep an eye on how the lighting works to avoid any hidden spike pits.
In the second half of the map, kill the skeleton enemies to light up the area nearby. As you climb up, you will need to defeat skeletons to see where the path forward is.
At the very top, head to the left to find a preparation room. Head to the right to reach...
BOSS: GENESIS
Genesis will fly back and forth across the map. On its way to the right it moves at a rather fast speed, and on its way back to the left it will stop and shoot three invulnerable shots at random heights towards you.
Genesis will also be accompanied by small star-like enemies, and several floating blocks. The star-like enemies won't damage you until they grow to a larger size and begin fluttering back towards to left.
The strategy for this fight:
After you finally take down Genesis, you can head to the next area, The Abandoned Facility. If you've defeated Oblivion already, you're ready to deal with The Aftermath.