The Evil Within guide: Chapter 14 - Ulterior Motives
Battle through the subway as you near the end of The Evil Within.
As you begin this chapter explore all the side rooms and passages in the subway. You'll find plenty of loot and a mirror so you can save progress and upgrade Castellanos.
One thing to note about this section is the abundance of spiked proximity bombs. You can trigger them and run away out of their blast radius, but be careful as they can be a pain in the ass.
As you continue deeper underground you'll eventually come to a garage door and an iron gate. There are some enemies to kill in the subway cars which you can take care of with sneak kills, and burn any bodies on the ground with matches for good measure. There are some traps in the subway cars too.
When you get to the gooey web set fire to it to continue. When you come across the electrical traps duck under one and use the lever to turn off the other. Keep following the path upstairs, pulling levers and disabling traps and you'll eventually arrive at a save mirror. Save the game, upgrade if you want to, then crawl into the nearby vent shaft.
When you drop into the sewer and follow the path you'll arrive at a room with water in the middle. Turn the valve to drain it and keep going forward. You'll climb a couple of ladders and set fire to another web, then arrive at a concrete tunnel.
There are two-headed enemies here, which you've encountered before. At a distance one shot from the Sniper Rifle puts these guys down for good. Burn any hanging bodies and take the battery-thing from the panel on the far wall. Backtrack a little to find the valve that was previously blocked by an electrical current. After you've triggered the cutscene, shoot the beast a few times in the face and it will drop you.
Further on you'll find an generator with an elevator and lever inside. To the right of the elevator is the puzzle and next to it the piece to solve it. Arrange the puzzle so that all the components are lit up, which will restore power to the elevator and kick off the boss fight.
When fighting Quell use your explosives first, which will prompt it to try and hide in the vents above. Look for the dripping goo that gives away its location and shoot it. If you shoot the spawning worms that come from it they leave behind extra ammo so you shouldn't run dry. When it attaches itself to the wall and turns invisible, hit it with everything you've got.
Once Quell is dead power up the elevator via the generator, take a ride, and follow the path onto the suspended subway. Ruvik will turn up, which is your cue to hot foot it until you're teleported and the cutscene begins.
When fighting the enemies connected to Ruvik, hit them with Freeze or Flash Bolts to stun them, then get in close to disconnect them with another attack. Once they are dealth with you can watch the cutscene and upgrade/save in order to face the final chapter.