Demon smoke

Smoke is substance use by angel and demons.

= Demon Smoke = Demons appear as a smoke in their incorporeal form, they manifest by possessing humans, alive or recently deceased, via demonic possession. Acheri demons are the only exception, as they are able to manifest from their smoke form into that of a little girl. When an exorcism is performed, this forces the demon to leave its vessel or meatsuit, and the smoke is usually seen pouring out of the person's mouth. In nearly all cases the smoke is black, although Crowley's smoke was shown to be red.[1].

Abaddon possesses the ability to partially enter a person, by sending a piece of her "smoke" form into the persons body to read their thoughts.

= Grace = Grace is a type of divine energy related to an angel's being. It's effectively what makes them angels; without it they are mortal. Anna calls its power "pure creation."[1] Removal of grace is considered a great taboo by angels; it is akin to disobeying orders and punishable by a death sentence, or in the very least torture and imprisonment. Uriel is able to take Anna's grace from the oak tree that it created when she fell. In turn she is able to re-imbibe it and return her angel status.[2]

Metatron takes Castiel's grace from him to use in a spell to cast all the angels from Heaven.[3] Without it, Castiel is human, although much like Anna he was still able to hear the angels on "angel radio." After living as a human for some time, he kills an angel called Theo and takes in his grace, and becomes an angel again.[4] It therefore appears that grace is not unique to an individual angel, and can be transferred, though Castiel seemed quite unsure whether taking Theo's grace would be permanent, or what powers he would have. The consequences of stealing another angel's grace was later revealed by Metatron, who told Castiel that his stolen grace was fading, and that once it was used up, Castiel would burn out along with it.

When angels leave their vessels a small amount of the angel's grace remains inside the vessel. Angel Lore says that "the departed shall remain, and the remains shall be the departed."[5]The Men of Letters believed that if the grace could be extracted, it could be used in a tracking spell to locate the angel the grace belonged to.