Threat Level Twilight

For Billie Keller, it's time to punch somebody in the mouth.
Losses have stacked up. Derik Cote and his crew have torn through DC, stolen magical artifacts, twisted science into weapons, and taken one of her own.
That ends now.
Step one: squeeze Derik's people until they crack.
Step two: dig up secrets he can't survive.
Step three: hit back-and keep hitting until he's gone. Preferably hard.
The problem? His army.
Elementals-frost, fire, lightning, force-and something worse waiting in the wings. Derik isn't just building power. He's upgrading it.
Billie's bringing everything. Her team, the pixies Onyx somehow convinced to join (no one's asking how), and every ally willing to stand their ground.
May it be enough.
And the most dangerous weapon in Derik's arsenal hasn't shown itself yet. That's never a good sign.
When magic turns deadly, the FBI's Magical Threats Division answers the call. And they don't do subtle.