Humans are the third branch of magical races, though they are the least recognizable. This is because the type of magic they manifest was internal. Evidence of this magical race's true identity is found in the fact that both humans and sidhe can both be acted on for good or ill by the other magical race, the djann and djinn.
The limitations of their type of magic would lend to them being dismissed and demeaned by the sidhe, whose magic manifest in a physical form. But just because the magic of humans was internal did not make it any less viable or useful. In fact, the fact that the magic manifest within made it that much more virulent and powerful.
When a human discovered his or her inner source of magic, and was able to tap it for constructive use, it was a source of the most immense power; all the more deep, potent because of it being held insight without release for the longest time.
The magic of creativity and imagination are potent forms if cultivated, and every human has this inborn and innate ability if harnessed and cultivated properly. It is through the actions of the djann and djinn who either deceive or empower humans in their cultivation of these powers.
And it is through the teaching and promotion of the art of alchemy to both humans and sidhe that the Blackburn brothers help each invested individual channel this magic.