At the start of the Trial, 4 random Hooks, as well as the Basement Hooks, are changed into Scourge Hooks:

The Auras of Scourge Hooks are revealed to you in white.
Each time a Survivor is hooked on a Scourge Hook, the following effect applies whenever you are farther than 24 metres from the hooked Survivor:
Accelerates the Sacrifice Process by 10/15/20 percent.

The Auras of regressing Generators are highlighted in white.

If the Regression progress is interrupted on a Generator, its Aura will be highlighted in yellow for 8/12/16 seconds.
Surveillance increases the audible range of Survivors Generator-repairing noises by 8 meters.

Your base Terror Radius is increased by 8 meters.

Whenever you are outside of a Chase, your Terror Radius is reduced by 16 metres while your Field of View is increased by 3/5/10 °.
Field of View gains do not stack.

After unhooking a survivor, all survivors who are at least 60/50/40 meters away from that hook have their Aura revealed to you for 4 seconds.