A Shadow Name is an expression of who the mage thinks she is in the Supernal World, without the Fallen, mundane person inside it. Most are only used when performing magic or meeting other mages, like a persona that can be adopted at will.
Mages take their Shadow Names very seriously. They are symbols, and therefore Supernal, influencing their bearers’ lives. A mage naming himself after a god, for example, would be able to use items relating to his namesake as magical tools, but might find his magical career influenced to force him into that identity, events eerily paralleling the myth-symbols he made his magical identity from.
Not every mage is re-enacting her namesake’s legend — not even most of them — but a Shadow Name is not something to be chosen lightly.
Some mages change their voices or body language so much that at first glance they’re unrecognizable when out of character.
Function
A Shadow Name serves two functions. First, it helps conceal the mage’s Sympathetic Name from enemy mages who might use that knowledge to cast spells on her Sympathetically. More importantly, though, it prevents the mage’s Nimbus from affecting those who only know her by her Sleeping identity.
So long as the mage practices magic within her Shadow Name, only those things close to her as a mage (her cabal, sanctum, apprentices, Dedicated tools, etc.) are affected by her Nimbus.
A Shadow Name’s protection works best, however, if a mage avoids using magic in the presence of the loved ones of his Sleeper life.
If he allows too much of a connection to form between his Shadow Name and his un-Awakened family and friends, they may yet fall under the influence of his magic.
Isolation
A Shadow Name is a representation not just of the mage themselves, but of their reformation and Awakening; it is a tangible reminder of the distance they have between themselves and the Sleepers in their life.
It is, unsurprisingly, a focus of the Sympathy the mage forms as they act under that name, but it is also their admission that they are now, fundamentally, disconnected from those who were once closest to them.
A distance that is only destined to grow.
Mage Society
Using a mage’s Sympathetic Name to address or refer to him except in the most intimate of friendships is considered offensively rude by the overwhelming majority of magical societies.
In some Orders, such as the Silver Ladder, Guardians of the Veil, and the Seers of the Throne, it’s a punishable crime.