A mythal is created by a circle of elven High Mages to protect and ward a large area with numerous powerful enchantments. A typical mythal prevents certain schools of magic from being employed, affects everyone within its bounds with certain magics, and may allow everyone or certain classes of people to call magical effects from the mythal as though using a magical item. It may restrict access of the warded area to certain classes of beings. For example, Silverymoon's mythal excludes evil dragons and forbids casting magic to teleport into the mythal. Creation of a mythal sometimes requires the willing sacrifice of the lead caster's life, a result that led to the first mythals being named after their creators. In addition, many mythal spells corrode over time, and if not maintained can become corrupted. This has occurred in Myth Drannor and resulted in the current state of that city.