You become obsessed with one Survivor.
Each time you hit a Survivor other than your Obsession with a Basic Attack, Save the Best for Last gains 1 Token, up to a maximum of 8 Tokens:

Gain a stack-able 5 percent Cool-down reduction on successful attacks per Token, up to a maximum of 40 percent.
Each time you hit your Obsession with a Basic Attack, Save the Best for Last loses 4/3/2 Tokens.

When the Obsession is sacrificed or killed, you can neither gain nor lose any more Tokens.
You can only be obsessed with one Survivor at a time.

The Entity blocks a window for 20 seconds after a Survivor performs a rushed vault through it.

The Hex effects persist as long as the related Hex Totem is standing.

3 seconds after injuring a Survivor by any means, Dissolution activates for 20 seconds.  While Dissolution is active, if a Survivor fast vaults over a pallet inside of your Terror Radius, The Entity will break the pallet at the end of the vault, and Dissolution deactivates.

Whenever a Survivor is put into the Dying State by any means, all other Survivors within your Terror Radius will scream and reveal their current location to you for 4/5/6 seconds.

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 hooking a Survivor, all other injured Survivors suffer from the Hemorrhage and Exhaustion status effect for 45 seconds.

Blood Echo has a cooldown of 60 seconds.

Exhausted prevents survivors from activating exhausting perks.
Hemorrhage regressing healing progress when not healing, and increases blood trails left by injured survivors.