Angel-killing bullets

Angel-killing bullets are bullets made out of melted-down Angel Blades that can kill all celestial and demonic beings. They are not effective against Archangels.

History
In "The Great Escapist", Crowley reveals his new invention, an Angel-Killing Gun which he produced by melting down angel blades. He demonstrated its effectiveness by killing Esper and wounding Ion. He also shot Castiel with a bullet in order to retrieve the Angel Tablet hidden inside his stomach.

Castiel used that same bullet he was shot with to kill Ion by forcing it into Ion's eye.

In "All Along the Watchtower", Castiel, Sam and Dean discover an alternate universe in which humans hunt angels and are equipped with guns loaded with angel-killing bullets.

When Dean tried to use the gun on Lucifer, the bullets prove ineffective.

Appearances

 * Season 8
 * The Great Escapist
 * Season 12
 * All Along the Watchtower

Trivia

 * Although not yet shown, the bullets are likely effective against everything that can be killed by an angel blade, like Hellhounds.