Doppelganger Series by Marie Brennan

When a witch is born, a doppelganger is created. For the witch to master her powers, the twin must be killed. But what happens when the doppelganger survives? Mirage, a bounty hunter, lives by her wits and lethal fighting skills. She always gets her mark. But her new mission will take her into the shadowy world of witches, where her strength may not be a match against powerful magic. Miryo is a witch who has just failed her initiation test... moreWhen a witch is born, a doppelganger is created. For the witch to master her powers, the twin must be killed. But what happens when the doppelganger survives? Mirage, a bounty hunter, lives by her wits and lethal fighting skills. She always gets her mark. But her new mission will take her into the shadowy world of witches, where her strength may not be a match against powerful magic. Miryo is a witch who has just failed her initiation test. She now knows that there is someone in the world who looks like her, who is her: Mirage . To control her powers and become a full witch, Miryo has only one choice: to hunt the hunter and destroy her. less

Revolution has come to Starfall. To some, Mirei is a savior. Born from the union of opposing forces, her existence offers a way to heal the division between warrior and witch, and brings powerful new magic into the world. To others, Mirei is an abomination. She overturns the ancient traditions of the witches, threatening their stability and corrupting their magic with an influence that should be destroyed. But even Mirei's power is not enough to prevent a civil war... moreRevolution has come to Starfall. To some, Mirei is a savior. Born from the union of opposing forces, her existence offers a way to heal the division between warrior and witch, and brings powerful new magic into the world. To others, Mirei is an abomination. She overturns the ancient traditions of the witches, threatening their stability and corrupting their magic with an influence that should be destroyed. But even Mirei's power is not enough to prevent a civil war. And while she struggles to reconcile Starfall's opposing factions, a more insidious threat is building within her -- because her newfound magic does not come without a price. less

When a witch is born, a doppelganger is created. Forthe witch to master her powers, the twin must be killed. Or so itwas believed for centuries . . . Once Mirei discovered that mergingwith a doppelganger gave a witch more power than killing them, thewitches at Starfall have been in an uproar (Doppelganger; 4/06). Herheresy goes against centuries of teaching-and the accepted practice ofmurdering their doubles... moreWhen a witch is born, a doppelganger is created. Forthe witch to master her powers, the twin must be killed. Or so itwas believed for centuries . . . Once Mirei discovered that mergingwith a doppelganger gave a witch more power than killing them, thewitches at Starfall have been in an uproar (Doppelganger; 4/06). Herheresy goes against centuries of teaching-and the accepted practice ofmurdering their doubles. On a quest to collect the survivingdoppelgangers, Mirei is unsurprised to discover that there are stillwitches at Starfall who side against her and her unorthodox ways. Butworse, her fellow hunter and closest friend, Eclipse, has beencaptured by these same witches-and has no choice but to swear a bloodoath to kill Mirei. If he fails his blood oath, he will die. With thewitches divided, and Starfall itself in the middle of a civil war,Mirei will have to choose between saving her friend and figuring out away to unite Starfall before it's too late. less