The Darkness' Fog was a gas-like supernatural substance which turned humans into Rabids. It was exclusively spread by Amara in order to make people see things from her point of view.
Sometime after Amara kidnapped Lucifer and began torturing him, she unleashed this fog at Hope Springs, Idaho. Many of the citizens were affected by the fog, and many of them died. Sam and Dean were alerted by the events happening in this town and rushed to discover the cause.
When the fog appeared to them, they gathered unaffected citizens and sealed them - as well as themselves - inside the police station. The fog however, managed to break through the duct tape and infect Sam, nearly turning him into a Rabid.
|“||She says it's a mirror. She's showing us all the truth. The light was just a lie!||”|
— Deputy Jan Harris
in Don't Call Me Shurley
The fog spreads similarly to natural fog, but differed significantly in its effects. Humans who came in contact with the fog turned into Rabids and can hear Amara's voice inside their heads. They also develop violent and aggressive behavior, often starting to murder other humans, and, as a result of her voice whispering incessantly in their heads, begin to share Amara's view of the world. Prophets were immune to the fog, as was Dean Winchester.
- Amara exterminated the population of several towns with the fog.
- Besides humans, it also kills animals.