Living Nightmare — Shannon K. Butcher

They are the Sentinels. Three races descended from ancient guardians of mankind, each possessing unique abilities in their battle to protect humanity against their eternal foes: the Synestryn. Now, one Sentinel's burning loyalty and love may prove to be her greatest weapons.

For nine years, Nika has had one goal: to save her younger sister from the Synestryn who hold her captive. Now the psychic bond Nika forged with her sibling is fading, and time is running out. But the one man who can unlock the power inside her left and never returned, leaving Nika alone to rescue a sister everyone else believes is dead.

Madoc swore to himself he would never enter Dabyr again. For his soul is nearly dead, and he fears what he might do to those he's sworn to protect -- especially Nika. If he accompanies her into the Synestryn realm, his forbidden desire for her may unleash the savage monster within him. But Nika's need to rescue her sister is soon becomes intertwined with her passion for Madoc, while the a key to victory in the war may be within her reach...