Fetcher Auls is what is commonly referred to as a "Magic Eater", a vampiric race of people who instead of feeding on blood or life-forces, they feed instead upon all things magical and sustain themselves on magic of all kinds. They are, likewise, immune to most if not all magic and so they make for very useful defenses during magic-based combat and war. Unfortunately, it is because of this that most of the Magic Eater race, called "Ve'gaul" in their native tongue, was committed to genocide through a number of different nations wishing to erradicate a steadily growing Magic Eater population - and military.
There are roughly only a thousand Magic Eaters left in the land of Valesia, though whether more remain elsewhere on the planet remains to be seen.
Fetcher Auls is apart of a Trio known among the Slave Trades as "The Fickle" which includes Tara Leif, Fetcher Auls, and Szule. He fell into the slave trade after he became an adult, roughly a few months after the genocide of his race was officially declared 'over' by the then-King and then-Queen of Valesia. Fetcher was the first of The Fickle to find Tara in the slave trades when she was still fresh to the collar, and he was the one who taught her how to hold her own against slaves and masters alike.