The Grey Wall

The Veil is the Aura of an ancient Evil that is located on an island somewhere west of Stakhlian. It is one of the old powers that used to run the world, until the 'Creator' defeated him and banished him. When Ismon/Omnis tried to heal his son, it was the demon Vantasvart's power that he summoned and with it he summoned the demon, weak as he was, as well. The demon now sits and gathers his power - this is done by pushing his aura and consuming man and turning them into mindless zombies that fight constantly.

The veil is slow to move, but the power is immense. It cannot go over mountains, as the Aura is too heavy to ride atop of thin air. It does travel fine above water, so one day the east cost will also be engulfed in the Veil, but as for now, mankind does not see or worry about it - as long as the West holds.