Guardians of the Past
Each mage in the realms has his own personal rune or symbol, which is used both to identify his own work and to protect his items. This symbol is unique for all active mages in the realms and remains with the particular caster until death.
A wizard chooses his symbol some time before reaching level four. Long lived wizards sometimes go through several different symbols during their lifetime, but many stay with the first sigil they chose. A caster may change runes at 10th, 15th, 20th, or 25th level. The inherent nature of the sigils prevents a caster from copying a sigil of another living wizard.
A heavy curse is inveighed against those who seek to use the sigils of other mages to their own ends, either with the intent of counterfeiting, fraud, or mischief making. The curse is said to come from Mystra herself.
Mystra also frowns upon the casters who refuse to identify themselves with a mage sigil. Only apprentices, hedge wizards, and weak dabblers of magic are not required to create their own wizard’s sigil. Any skilled wizard who shuns this task, will be politely asked by Mystran clergy and other practitioners of the art to comply. Failing that, a rebellious wizard may soon discover their spells going awry, always to their detriment.