Mortal Demon by Tia Didmon

A Murder. A Decision. A Demon King.

Riley and Colton’s bonding preparations turn into a hunt for a murderer when a clan member is found dead. Clues point to a traitor within their clan, causing dissension with the other shadow shifters. But further investigation leads them to a fertility clinic run by demons where the magnitude of horrific experiments is discovered.
In an attempt to save the endangered shadow shifter world, Riley and Colton turn to a priestess for help. But after Riley is abducted by the person she trusts the most, she learns the true power of the demon king’s blood.

Will Riley make the ultimate sacrifice to save her family or become the king’s lethal weapon against the human race?