Warning: Spoilers for Batgirl #1Cassandra Cain's Batman's no-kill rule cements her as such. Since being introduced as an assassin, Cassandra has evolved into Batman's perfect successor by following his practice of sparing lives. Her team-up with her assassin mother showcases how Cass fits into her father's legacy, as Batgirl solidifies her devotion to Batman's cause and proves that she is his daughter before she is Lady Shiva's.

reunites Cassandra with her mother, Lady Shiva, when a mysterious group of ninjas goes after her. This reunion isn't joyous for Cassandra due to the complicated relationship they share, as she reiterates throughout the issue that she does not consider Shiva her true mother. Her loyalty now lies with Batman, which she confirms by saying: "I am Batman's daughter by choice. I know how to kill. I hold back by choice."

Batgirl's loyalty to Batman is intrinsically tied to her loyalty to the "no-kill" rule she learned from him. Through deciding not to kill, Cassandra Cain chooses Batman over Lady Shiva and thereby confirms who her true parent is in DC lore.

"No Killing": Batgirl Shows Her Loyalty to Batman's Code Over Lady Shiva's

Cassandra Cain Refuses to Let Her Mother Kill, After Learning From Batman

Batgirl’s refusal to kill is a lesson she learned from Batman, and it’s become a central aspect of her character. When Lady Shiva approaches Cassandra to inform her of the threat that's seeking her out, rather than hearing her mother out, she fixates on the fact that her mother has killed an innocent bystander. This death leads to her initially rejecting to speak with Shiva at all and attempting to leave the premises, which goes to show how Batgirl values her moral stance above all else, even when Shiva insists that there's danger on the horizon.

Batgirl's unyielding dedication to preserving life doesn't just extend to innocents.

Lady Shiva is a deadly assassin who has no issue with killing those who stand in her way, and so she and her daughter are diametrically opposed. She doesn't value the sanctity of life, while Cassandra calls her out for killing. No explanation is enough for Cass to excuse her actions as she repeats with conviction, "No killing." Batgirl's unyielding dedication to preserving life doesn't just extend to innocents, as it includes her assailants. This insistence on mercy reveals how much Cassandra has changed since her introduction, and it's all thanks to Batman's influence.

Cassandra Cain Was Raised to be a Killer Until She Found Batman

Batgirl's Origin as an Assassin Trainee, Explained

Before she became Batgirl, Cassandra Cain was supposed to be every bit the killer that her mother is. Her father, the vile David Cain, treated her as an experiment to become the ultimate assassin. David deprived his daughter of the ability to speak or read, instead forcing her to read her opponents' most minute mannerisms and communicate with her fists alone. Cassandra's solitary purpose for her existence was to kill, a stark contrast to the mission statement she abides by today. Batgirl's twisted origin story culminates in her escaping David's clutches and taking refuge with Batman in search of a different way of life.

Cassandra Cain made her first appearance, during the massive Batman Family "No Man's Land" event, in 1999's Batman #567 by Kelley Puckett, Damion Scott, John Floyd, Gregory Wright, and Todd Klein, available now from DC Comics.

During her traumatic upbringing as an assassin, Cassandra never had the luxury of choosing whether to kill or spare those she fought. All she could do was obey orders without questioning the consequences for herself and others. Now, as Batgirl, Cassandra gets to dictate her own path without anyone else's input weighing her down. Cassandra acknowledges that she’s capable of killing, but she makes the active choice not to - because now she gets to define who she is, and she's chosen to be a hero in Gotham who stands by Batman’s code instead of David Cain's.

Batman's No-Kill Rule Separates Batgirl from Her Birth Father

Batgirl Leaves Her Assassin Roots Behind Thanks to Batman's Influence

such as with Darkseid, but the difference between a universal threat and a low-level criminal is vast. Batman may be the night, but his goal is to protect those in the dark rather than become another monster for them to fear, and Batgirl inherits this goal from him.

It takes time for Batman's moral code to take root within Cassandra due to her troubled past, and her moment of truth finally arrives in 2008's Batgirl #6 by Adam Beechen, Jim Calafiore, Jack Purcell, Nathan Eyring, and Sal Cipriano. Batgirl engages in an emotionally-charged battle with David Cain, and she considers leaving him to die before ultimately trying to save him. She fails in the end, but the fact that she tries at all demonstrates that she's chosen Batman's teachings over David's. Cassandra's adherence to his no-kill rule leads to Bruce officially adopting her, making him her father in both an emotional and literal sense.

Batgirl's Tentative Alliance with Her Mother Puts Her Morals to the Test

Cassandra Cain Teaming Up With Lady Shiva Doesn't Cancel Out Her Loyalty to Batman

Even when begrudgingly teaming up with Lady Shiva, Batgirl holds fast to the morals that were ed down to her from Batman. She gets a say in her own destiny now, and she has selected the path of mercy alongside the other heroes of the Bat-Family. Working with an assassin isn't ideal for Cassandra, but this alliance isn't being forced on her. She chooses it, just as she chose to follow her no-kill code. She chooses to call Lady Shiva her mother and to be her daughter in return for this one night, as she remains Batman's daughter on every other night.

Batgirl's alliance with her mother isn't without strings, evidenced by the ground rules she firmly establishes throughout the issue. She doesn't let killing slide, and the only way she can be swayed to Lady Shiva is if she holds back for the duration of their team-up. As such, her acceptance of being the assassin's daughter is no moral backslide on Cassandra's part. While she physically fights beside her mother, she still aligns with Batman as opposed to Lady Shiva. First and foremost, Batgirl is the child of Batman in every way that matters, and her birth parents can't take that from her.

Batgirl #1 is available now from DC Comics.