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.

Unlocks the Self-Care ability, allowing you to self-heal without needing a Med-Kit at 25/30/35 percent of the normal Healing speed.

After hitting a Great Skill Check while repairing or healing, Hyperfocus gains 1 Token, up to a maximum of 6 Tokens
For each Token, the following stack-able effects are applied:

Increases the Skill Check Trigger odds by +4 percent per Token.
Increases the Skill Check Rotation speed by +4 percent per Token.
Increases the Skill Check Bonus progression by 10/20/30 percent of its base value per Token.
Hyperfocus loses all Tokens when succeeding a Good Skill Check, failing a Skill Check, or if the action is interrupted by any means.

Increases the Success zone of Great Skill Checks while Repairing and Healing by 10/20/30 percent when in the Injured State.

After repairing Generators for a total of 33 percent, Wiretap activates:

After repairing a Generator for 3 seconds, press the Active Ability button to install a Wiretap, which stays active for 60/70/80 seconds.
The Auras of trapped Generators are revealed to all Survivors in yellow.
When the Killer comes within 14 metres of a trapped Generator, their Aura is revealed to all Survivors.
Damaging the Generator destroys the Wiretap.

After triggering your third Protection Hit, Mettle of Man activates:

While injured, Mettle of Man shields you from going down the next time you take damage.
Healing back to full health will reveal your Aura to the Killer whenever you are farther than 12/14/16 metres from them.
Mettle of Man deactivates the next time you are put into the Dying State.

Increases the odds of becoming the Killers initial Obsession by +100 percent.

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