Fighting the Shadows

My book follows the life of a young man (eighteen to nineteen) as he works for a secret agency in the protection of humankind against the forces of supernatural creatures and the prevention of mankind learning about the real supernatural world. (Every supernatural creature comes from a city kilometres underground-vampires, giants, Cyclops, demons, and so forth.) This agent is code named Black because he has the power to transform to a full-sized black-scaled dragon with red eyes and purple flames. But the first time he transformed, he was trying to protect a little girl from lava lizards, huge one-ton lizards that spit lava. His powers went out of control, and he burned up the little girl. Now, he does not let a lot of people close. One night, he comes across a work site where four teenagers are being attacked by a shadow wraith (a creature of darkness that feeds on the life force of any living thing). After the attack, Agent Black takes them back to this base to get them checked, where they meet Doc, an elven doctor, and the commander, an immortal woman that has lived for more than a thousand years, and she is the head of the SNPA, the Supernatural Protection/Prevention Agency (depends on which world you come from). Soon after all this, they learn that four teenagers have the same power as Black and have the power to change into dragon (three guys, one girl-ice, earth, and fire guys, and golden magical dragon girl) and are asked to learn from Black to control their powers and protect the secret of this world.