Gifted Humans.

As previously noted. Humans generally do not have any sort of magical Powers. However this is the exception to that rule. Some humans somewhere in there past may have a magical Grandparent or two. And while that magical trait may not always pass down from parent to child it can suddenly reoccur in a human now.

The other is rare and only a small handful at a time end up with having it and not everyone in the same family. One daughter out of three kids can show up having magic with not trace of the Mystic or Mysterian races in there blood line anywhere.

Once such Example was the Dark Mage Severin born Originally when the world was young and just starting out he fell pray as a magic user to a dark dragoness who enslaved and tortured him twisting his views on things. Due to the naturally occurring magic in his blood he lived a long time and when he would have died he had come across a shard of magic which extended his time even further. Not all humans born with magic are evil or bad but they are extremely rare. Out of the thousands of Humans on the world they may make up roughly a couple of hundred at most. And many hide there magics in fear of being out-casted from the Human race.