The Veil
Bobby: Well you've got, just over five hours to go? You're piercing the Veil, Dean. You're glimpsing the B-side.
Dean: A little less new age-y please.
Bobby: You're almost Hell's bitch. So, you can see Hell's other bitches.
– Bobby and Dean, 3.16 No Rest for the Wicked
The Veil appears to be the plane of existence on Earth that ghosts, demons, hellhounds and reapers are able to inhabit; and in the case of angels and demons occupying vessels, are able to pierce through and perceive the Veil. Symbols such Enochian runes/warding can be painted and hidden within the Veil, and can only be visible to those who can pierce/inhabit it.[1] A human will begin to pierce through the Veil once a crossroads demon contract is up, allowing them to see hellhounds and the true faces of demons.[2] Piercing the Veil can be incredibly taxing for a spirit, and takes a lot of concentration. In addition to Heaven, Hell and Purgatory rogue reapers appear to have secret ways in and out of the Veil.[3]
The ancient Celts believed that October 31st was the one night of the year where the Veil was thinnest between the living and the dead.[4] They used the night to appease the demon Samhain, who was able to summon spirits (among other supernatural entities) from the Veil onto the earthly plane.
It is revealed since Metatron enacted his spell, Heaven has been locked down, forcing all spirits to remain stuck in the Veil at the sites of their deaths.[5]
