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Born-Specialized Magicians (BS 魔法師) known as BS ability users, they can also be called innate ability users or innate magic specialists. This is due to the fact that they excel at a particular ability, BS magicians can use other magic, but they won't be as good as them as other magicians. Mainly because they exceed in their main magic. 
The unique abilities of BS Magicians are practically impossible for others to imitate. Even if someone were to use the ability, they wouldn't be able to replicate the same level of quality as the BS Magician. If properly matched with their specialty, they often outperform generic "omnipotent" Magicians. 
BS Magicians are viewed by society at a lower standard than that of ordinary Magicians.