Each time you hook a Survivor, Leverage activates and gains 1 Token, up to a maximum of 10 Tokens:

For each Token, the Altruistic and Personal Healing speeds of Survivors are reduced by a stack-able 3/4/5 percent for the next 30 seconds, up to a maximum of 30/40/50 percent.

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 Survivor suffers from the Hemorrhage and Mangled Status Effects until healed.
Upon being healed, the Survivor suffers from a 10/13/16 percent Action Speed penalty to Healing and Repairing until they are injured again.

The Scratch Marks left by Survivors spawn slightly/moderately/considerably closer together.

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.

When you search a locker, the auras of all Survivors within 8 meters of any lockers are revealed to you for 5 seconds.

This perk has a 30-second cooldown.

When a Survivor heals another  Survivor for one health state at least 32 meters away from the Killer, the Survivor performing the healing action will scream, revealing their location and activating Deathbound for the next 60 seconds.  During that time, the Survivor will suffer from the Oblivious status effect when further than 8 meters away from the healed Survivor.

Oblivious prevents the Survivors from hearing or being affected by the Killers Terror Radious.