Holy Oil

"When the oil burns, no angel can touch or pass through the flames, or he dies."

- Castiel

Holy Oil is a very rare substance that can be found in Jerusalem. A circle of burning holy oil is so far the only way to trap a celestial being. It makes its first appearance in Free to Be You and Me when Castiel brings it back from Jerusalem to trap Raphael. The angel will not be able to leave the circle. It should be noted that a circle of holy fire is not the equivalent of a devil's trap. When inside the circle, the angel still has use of some of their abilities and are able to move, they merely choose not to leave the circle out fear of touching or passing through the holy fire. If an angel touches or passes through/over holy fire, then not only will the human vessel be destroyed and die, the angel will be killed as well.

Michael, however is resistant to the holy fire and could not be killed by it. This is seen in Swan Songwhen Castiel throws a holy oil cocktail at him. This is most likely because he is the most powerful Archangel. The Holy fire is still painful for him and can temporarily banish him. A Holy Oil molatov would probably kill any other Angel.

It's likely the oil can burn forever until it is extinguished with water, since Gabriel fears being trapped forever in the holy circle (however, he may not have meant this literally but, as he's immortal, it must be a long time to worry him).

It is currently unknown if a "mutated Angel" (such as Castiel when he had absorbed all the souls of Purgatory) can be bound by a burning circle of it or killed by touching it.

Though Holy Fire cannot kill demons, it will cause them extreme pain, as demonstrated when Castiel threw Meg into Holy Fire.

Angels who have been attacked with holy fire are:

 * Castiel
 * Raphael
 * Michael
 * Gabriel
 * Balthazar