Mythal
From Forgotten Realms Wiki
Mythal is a powerful epic level magical effect, created by a circle of elven High Mages to protect and ward a large area with numerous powerful enchantments. They work by creating an area wherein the normal rules of magic no longer apply. A typical mythal prevents certain schools of magic from being employed while empowering others. It may restrict access to the warded area to certain classes of beings. For example, Silverymoon's mythal excludes evil dragons. Creation of a mythal sometimes requires the willing sacrifice of the lead caster's life, a result that lead to the first mythal's being named after its creator. 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.
