- Accessible from the Eastern and Western side of the central hill in the Outskirts.
- Access is only at riverbed level.
- Go into the tunnel and follow it through to the large middle room.
- There is a doorway on the other side, do not go through it.
- Inside this room, look around to spot the tunnel leading deeper in.
- Go inside that tunnel.
- Follow the passage into the pipe room, jump down to the floor below the walkway you are on, past the pipes.
- This will lead you into the Lost Sector itself.
- Clear out the first few Dregs and Vandal.
- Go into the room and turn to the right.
- This leads to a hallways with downward stairs.
- At the base of the stairs, the hallway splits forward, right, and left.
- To the left is an empty chamber some Fallen might try to escape into.
- Going forward leads to a large chamber with Dregs inside it.
- There is likely one buy the door with many more deeper in and a Vandal up on the walkway.
- This room connects to the boss chamber but there are a lot of Fallen deeper into it.
- To the right is the boss chamber.
- In here you will encounter the boss, Drekthas, Metal Captain, and their numerous Shanks, Dregs, Vandals.
- To access the cache in the very back of the Drain, you will need to kill.