Veil

The Veil was a boundary that separated the material plane of existence, from the realm of raw magic. Every mage drew from the realm beyond the boundary, but it was the veil itself that allowed creatures from the material plane to cast spells. The raw magic on the other side of it could only be used by the creatures that dwelt within that plane of existence. The entirety of Ayvindor is touched in some way by the Veil, and protected by the malevolent beings that wait for unwary mages, ripe for possession. Schools of magic, referred to as 'Arcanums' exist throughout the world.

Origins
The origins of the Veil stem from the early days when the elves first walked the land and dragons soared through the skies. Dragons, being creatures of magic, were unnaffected by the existance of the realm of raw magic that surrounded the world. However, the elves and other early peoples were unable to properly control the raw power that surrounded them and flowed into them when mages drew on magic.

The Veil was brought into effect by the god Ilumar, who was known as the god of both magic and wisdom.