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

The Auras of Scourge Hooks are revealed to you in white.
Each time a Survivor is unhooked from a Scourge Hook, the following effects apply:

The Auras of all other Survivors are revealed for 5/6/7 seconds.

Any Survivor performing a rushed action within 48 meters of your location has their Aura revealed to you for 6 seconds.
Im All Ears can only be triggered once every 60/50/40 seconds.

Any Survivor repairing a generator suffers from the Blindness and Exhausted status effect.  If the Survivor is already Exhausted, their status effects timer will be paused.

Both status effects linger for 5 seconds after stopping repairs.

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.

You become obsessed with one Survivor.
Each time a Generator is completed, the following effects apply:

Reveals your Aura to the Obsession for 5/4/3 seconds.
All Survivors locations are revealed to you for 3 seconds.
Once the Exit Gates are powered, the following effects apply:

You are granted the ability to kill the Obsession by your own hand.
The Obsession suffers from a permanent Exposed Status Effect.
You can only be obsessed with one Survivor at a time.

The Auras of Survivors, who are healing or being healed, are revealed to you when they are within a range of 20/24/28 meters.