In the Chrestomanci series
" is one of the classifications of magic-user recognised in World 12A
of the Related Worlds
. There are no Mages in 12A itself, only in the worlds of Series One
. They have very powerful magic, although how it compares in power and kind to, say, enchanter
's magic (the most powerful kind found in 12A), is not clear.
Chrestomanci attends the Conclave of Mages in Series One in "Stealer of Souls".