Thorn of Sorrow by Lynn Hagen

Some men are forged in fire. Others are born from the abyss.
I am Giovanni Winterhaven—harbinger of chaos, dealer of death. Even darkness knows when to fear its own monster. The whistle of my blades has razed empires and felled kings. My heart? Long buried in the ruins of my past.

And then I met him. A fire that refuses to be extinguished, a storm that shakes the foundations of everything I have built. He should have been insignificant, a fleeting moment in my long and bloody existence. Instead, he has become the one thing I cannot live without.
The one thing I will not lose.
I will rip my own darkness apart if it means giving him even a sliver of light. He is my solace. My salvation.
For him, I would betray my nature.
For him, I would let the world burn.
For Kyson, I would risk my soul.