Angel Ward

Angel wards are enochian-based symbols that prevent the entry of an angel from a certain location. The wards vary in appearance. Alastair, a demon, used complex symbols inscribed in circles. These runes were invisible to the unaided eye. Hunters, and Dr. Visyak, a purgatory native, used sigils that look more simplistic, drawn with chalk, or a blood-like substance. Crowley used runes posted on the four general directions of a building, and required disabling all four before an angel could enter the building. Crowley complemented the wards with other symbols that prevented Castiel from reaching his full strength.