In your countless years in The Fog, you have seen it all, and when you are focused, you can remember most of it too. Succeeding a Great Skill Check while repairing a Generator reveals the Killers Aura to you for 4/5/6 seconds.

Increases your Repair speed by +15 percent for each other Survivor within 4 metres of your location, up to a maximum of +45 percent.
This effect is also applied to all other Survivors within that range.
Grants 50/75/100 percent bonus Bloodpoints for Co-operative actions.
Survivors can only be affected by one instance of Prove Thyself at a time.

Unlocks potential in your Aura-reading ability:
Each time a Generatoris completed, Dark Sense activates:

The Aura of the Killer is revealed to you for 5/7/10 seconds, as soon as they come within 24 metres of you, after which Dark Sense deactivates.

While healthy and healing another Survivor without using a Med-Kit, press the Active Ability button to activate For the People:

Trades 1 Health State with the other Survivor.
Heals a Survivor from the Dying State to the Injured State.
Heals a Survivor from the Injured State to Healthy.
You become injured and suffer from the Broken Status Effect for the next 80/70/60 seconds.
You become the Killers Obsession, if not already.
Lowers the odds of becoming the Killers initial Obsession by -100 percent.
The Killer can only be obsessed with Survivor at a time.