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.

Any Survivor who blinds you or stuns you using a Pallet becomes the Obsession.
Anytime your Obsession switches to another Survivor by any means, that Survivor then suffers from the Oblivious Status Effect for 40/50/60 seconds and their Aura is revealed to you for 4 seconds.
You can only be obsessed with one Survivor at a time.

When carrying a Survivor, Starstruck activates:

Survivors suffer from the Exposed Status Effect while in your Terror Radius.
The Status Effect lingers for 26/28/30 seconds after leaving your Terror Radius.
After hooking or dropping the carried Survivor, Starstruck deactivates:

The Status Effect persists for 26/28/30 seconds for any Survivor inside your Terror Radius at that moment.
Starstruck has a cool-down of 60 seconds once the Survivor is no longer being carried.

The Aura of a Survivor entering the Basement when you are at least 32 meters away is revealed to you for 3 seconds.
Territorial Imperative has a cool-down of 30/25/20 seconds.

Whenever you put a healthy Survivor into the Injured State, all injured Survivors suffer from the Oblivious Status Effect for 20/25/30 seconds.
Hysteria has a cool-down of 30 seconds.

"Each time the Obsession loses a Health State, Remember Me gains 1 Token:

Increases the Opening time of both Exit Gates by 4 seconds per Token, up to a maximum of 8/12/16 additional seconds.
The Obsession remains unaffected by this penalty.
You can only be obsessed with one Survivor at a time."