The worlds of Control and Alan Wake collide with the AWE extension of the old one and, with it, cause a new danger to the environment. Darkness - an oozing black substance - appears in the investigation area of the Oldest House, and like the Mold and Plant quests, you receive the Burn the Dark mission from resident janitor Ahti.
There are three puddles of darkness to burn in three areas of the Investigation Area. You'll know they're nearby if you see a light you can pick up on, or hear a faint howl. You have to shine light on the darkness to eradicate it. Once all three areas are cleared, you will receive rewards for your efforts.
Service ducts
There are three pieces of darkness to be removed from the service ducts. All three are at ceiling level, so you don't have to search for them. There is a light at the end of the tunnel, next to a hole in the ground that you will drop, which you can grab to burn away the darkness.
Eagle Limited AWE
After defeating Shaded Hartman in this area, you can search and destroy the Darkness patches. First, take the elevator to the back of the room to catch a light in this first floor office.
For the first piece of Darkness, head to the Altered Item train car and look to your right above the orange mobile lab. Levitate and rush to its roof and look up. Shine light on a metal grid here to destroy this darkness.
The other two are located on the rafters high up in the room. Levitate towards the metal beams above the wagon, then levitate and dash onto the catwalk in front of you. Head to the left to destroy a piece of Darkness, then come back along the catwalk to find the other in a shady corner.
Utility corridor
The last three pieces can be found here. You can access this area from the control point of the deck. Levitate off the turntable and dash through the glass to a desk above. Take the light on the table to your left.
Go to the office behind the light to burn off the first piece of darkness. Next, head to the utility corridor and burn the darkness in front of you. Finally, follow the hallway to the next open door. Immediately turn left, head towards the back wall and burn the darkness on crates on wheels.
