Dead by Daylight

Nightfall is an ability of the Dredge. During a match you'll notice a circle growing around the survivor icons on the HUD. When this circle is full Nightfall will be initiated. Your view goes from color to black and white. Survivors become pure white making them much easier to spot if they are hiding in bushes. As the description states, you must down survivors during Nightfall. Pretty straightforward.

A few notes

Nightfall will power up quicker if survivors are injured, concordantly the more survivors injured the quicker the gauge fills. I recommend keeping the survivors injured till Nightfall is charged. Then you can knock down 2 or 3 with a single blow when it triggers. Obviously easier and quicker if you can get a spare account or two into your lobby