The Dream Hunter — Sherrilyn Kenyon

IN THE ETHEREAL WORLD OF THE DREAM-HUNTERS
Condemned by the gods to live eternity without emotions, Arikos can only feel when he's in the dreams of others. For thousands of years, he's drifted through the human unconscious, searching for sensation. Now he's finally found a dreamer whose vivid mind can fill his emptiness.

THERE ARE CHAMPIONS WHO FIGHT TO PROTECT THE DREAMER....
Dr. Megeara Kafieri watched her father ruin himself and his reputation as he searched to prove Atlantis was real. Her deathbed promise to him to salvage his reputation has now brought her to Greece where she intends to prove once and for all that the fabled island is right where her father said it was. Instead, she finds a stranger floating in the sea--one whose face she's seen many times...in her dreams.

AND THERE ARE DEMONS WHO PREY ON THEM.
What she doesn't know is that Arik holds more than the ancient secrets that can help her find the mythical isle of Atlantis. He has made a pact with the god Hades: In exchange for two weeks as a mortal man, he must return to Olympus with a human soul--Megeara's.