Black Lion’s Bride by Lara Adrian

A beautiful assassin is sent to kill the king, but her secret mission is thwarted when she crosses paths with Lionheart’s best warrior. Can hate turn to love when her life depends on destroying the enemy?

She was a dangerous beauty, the enemy he couldn’t resist . . .
Daughter of the King of the Assassins, Zahirah was trained to be as deadly as she is beautiful. When she steals into the desert camp of the English army, she has one goal: to banish the crusaders from her homeland by murdering King Richard the Lionheart. Her deceptive strategy delivers her into the hands of the enemy—and puts her at the mercy of the dashing Black Lion, Sebastian of Montborne.

Fighting for peace in a dangerous, exotic land, Sebastian never dreamed that the tides of war would bring him a mysterious beauty in need of his protection. Nor could he guess that the lady who ignites his heart is the very enemy he has sworn to destroy on behalf of his king. Caught in a deadly game of passion and deception, their unbidden love could cost them their lives. . . .

This full-length historical romance is part of the Warrior Trilogy, but also can be enjoyed as a standalone novel.