Each time a Survivor other than yourself is killed or sacrificed, Sole Survivor gains 1 Token, up to a maximum of 3 Tokens:

Each Token grants a stack-able radius of 20/22/24 metres within which the Killer is unable to read your Aura, up to a maximum of 60/66/72 metres.
Once you are the last Survivor standing, you benefit from the following effects:

Increases your Repair speed of Generators by +75 percent.
Increases your Opening speed of the Exit Gates and the Hatch by +50 percent.
Increases the odds of becoming the Killers initial Obsession by +100 percent.

The Killer can only be obsessed with Survivor at a time.

Increases your Crouching Movement speed by 90/95/100 percent.

After repairing Generators for a total of 70/60/50 percent, Flashbang activates:

Enter a Locker while empty-handed and press the Ability button to craft a Flash Grenade.
The Flashbang is left behind when escaping the Trial.

When you unhook a Survivor, the rescued Survivor benefits from the following effects for 4/6/8 seconds:

Scratch Marks and Pools of Blood are suppressed.
Additional 7 percent Haste Status Effect, boosting their Movement speed.
Guardian reveals the Killers Aura to you for 8 seconds.

Whenever another Survivor is hit with a Basic Attack or Special Attack within 16 metres of you, Self-Preservation activates:

Scratch Marks, Grunts of Pain when injured, and Bleeding are suppressed for the next 6/8/10 seconds.

Unlocks potential in your Aura-reading ability:
The Auras of closed Chests and dropped Items in the environment within 16/24/32 metres of your location are revealed to you.
Grants a considerably better chance at finding an Item of a higher Rarity from Chests.