Veil

"Gossamer strands only stand between this world and home. Feel it?"

- Sophia Dryden

The Veil is a metaphysical barrier that exists between the physical Thedas and the Fade. Neither spirits nor mortal beings can easily pass physically through the Veil, but the consciousnesses of most mortal dreamers and all mages are a different matter (though the average dreamer is unlikely to ever be aware of such 'travels').

The Veil is not an object - it cannot be touched or seen. It is a metaphor used by mortal scholars to explain the interactions between the two different realities.

Tears
It is theorized that the Veil tends to be weaker in places that feature, or have experienced, extensive death or use of magic. It is also revealed that the Veil is thinned in places with Red Lyrium. What is known for sure is the use of blood magic can allow the Veil to be torn so that demons may physically pass through it into the physical world. Areas that can be seen or felt where the Veil is thin are usually referred to as "tears" in the Veil, in keeping with the fabric metaphor. In fact, when the Veil itself tears it makes a sound like ripping cloth.

Known instances of the Veil being torn

 * The Veil gets torn multiple times during the events of Dragon Age: Inquisition, the largest being referred to the Breach. The Inquisitor is tasked with investigating the cause.

Closing a Tear
"Mending" these Tears, i.e. strengthening the Veil, is extremely difficult, if at all possible. Depending on the level of damage done to the Veil, it can be closed through several methods. For example, in Soldier's Peak, either Sophia Dryden or Avernus can accomplish such a mending, as Avernus is an expert on the Fade and Sophia is possessed by a powerful demon who crossed the Veil. The Warden-Commander can mend Veil Tears in both Dragon Age: Origins - Awakening and Witch Hunt - in this instance it is done by killing powerful spirits or demons. The Tear caused by Saarebas in Dragon Age: Redemption was closed after the artifact used to open it was destroyed.