Doomsday Brethren Series 1-3 by Shayla Black

Tempt Me with Darkness (Doomsday Brethren #1)
As soon as Marrok sees Olivia Gray's dark windswept hair and burning violet eyes, he's sure they've met in eons past. He's felt her soft gentle curves writhing in pleasure beneath his own hard powerful body...Morganna! For centuries, towering Marrok, once the mightiest of King Arthur's warriors, has endured a terrible curse cast upon him when he spurned the witch.
Olivia shares a mystical - and irresistible - connection with brooding Marrok. Soon after the sexy warrior appears in her erotic dreams, he abducts her, demanding she uncurse him. Their intense passion is more powerful - and intimate - than either of them has ever known. Olivia may be the key to unlocking the diary that will break Morganna's hold on his life. But in the wrong hands, the book also holds the power to destroy all magickind. As they search for answers, a ruthless wizard returned from exile is building an army of evil. When he discovers Marrok and Olivia have the diary, only their love - with the help of a powerful group of magical Brethren - can save them.

Fated (Doomsday Brethren #1.5)
Kari Keswick and Ronan Wolvesey burned for one another, but a deadly family curse targets their love with destruction. Will magic tear them apart?

Seduce Me in Shadow (Doomsday Brethren #2)
Ex-marine Caden MacTavish has shunned his magical heritage all his life, but he will do anything to heal his desperately ill brother, a Doomsday Brethren warrior in mourning for his missing mate. Posing as a photographer, Caden must convince firecracker tabloid reporter Sydney Blair to reveal the source of her recent exposé on a supernatural power clash. Unfortunately, keeping his hands off the sizzling redhead proves as hard as getting them onto the potent and mystical Doomsday Diary he discovers at her bedside. A bloody rebellion led by an evil, power-hungry wizard is imminent. If Sydney divulges the book's existence, she will jeopardize magickind's most deeply guarded secrets and become the ruthless wizard's number one target. Caden has never trusted magic's cruel and dangerous powers, but he will protect Sydney with his life and magic — even if it means risking his heart.

Possess Me at Midnight (Doomsday Brethren #3)
As a mysterious dark cloud drains the life of her beloved brother, Doomsday Brethren leader Bram, Sabelle Rion can think of little else. Still, every time she meets Ice Rykard’s intense green gaze, her body aches with need for the sexy warrior. Their attraction is explosive, incredible—and forbidden. As dangerous as he is unpredictable, Ice is her brother’s sworn enemy. But as Bram weakens, a more sinister force is gaining power. Evil Mathias and his ruthless Anarki army are on a bloodthirsty hunt for the Doomsday Diary. Sabelle must guard the potent book with her life—and Ice vows to protect the beautiful witch with his. Duty demands that Sabelle deny her lover’s fiery call of possession and mate with a man who can sway the magical Council against the impending rebellion. With the fate of magickind hanging in the balance, will she forsake the burning desires she can’t ignore or turn her back on her people for the courageous man she can’t resist?