Performing the Damage Generator Action on a Generator activates Trail of Torment:

Grants the Undetectable Status Effect until the Generator stops regressing or a Survivor is damaged by any means.
The Aura of the damaged Generator is revealed to all Survivors in yellow.
Trail of Torment has a cool-down of 80/70/60

After a generator is repaired, The Entity blocked the generator with the most progress for 30 seconds.  You see its white aura during this time.

"Survivors receive a 2/4/6 percent Regression penalty on Failed Skill Checks for Repair and Healing actions.
Hex: Huntress Lullaby grows in power each time you Hook a Survivor, gaining 1 Token, and affecting Repair and Healing Skill Checks:

1 Token: shortens the time between the Warning sound and the Skill check by -14 percent.
2 Tokens: shortens the time between the Warning sound and the Skill check by -28 percent.
3 Tokens: shortens the time between the Warning sound and the Skill check by -42 percent.
4 Tokens: shortens the time between the Warning sound and the Skill check by -56 percent.
5 Tokens: disables the Warning sound.
The Hex effects persist until its Hex Totem is cleansed."

Each time a generator is repaired, all windows and vault locations within 32 meters of it are blocked for all Survivors for the next 30 seconds.