The daughter of David Cain and Sandra Wu-San (Lady Shiva), Cassandra Cain was conceived and trained from birth with the intention of creating the perfect bodyguard for Ra's al Ghul. After many unsuccessful attempts to train children from birth in martial arts to make them inculcate it like a native language (the most successful being The Mad Dog), David Cain, then a member of Ra's League of Assassins, decided the right genes were necessary to create this "One Who Is All". With Ra's go ahead Cain searched for the perfect mother for this child, finding her in the Wu-San sisters of Detroit, who practiced martial arts with each other nearly every moment of their childhood in a type of sister's language. Cain sympathized with the younger sister, Sandra, when he noticed that she held back out of love for Carolyn. To "help" Sandra reach her full potential, Cain murdered Carolyn, then lured Sandra into an ambush by the League of Assassins, where he defeated her. Cain spared Sandra from death on the condition that she bear his child, and leave her for him to raise. Awed by the potential heights she could reach in her physical talents now that Carolyn was gone, Sandra agreed to Cain's bargain in order that she might go on to become the unstoppable force of nature known as Lady Shiva: creator and destroyer. Shiva's hope for her child was that she might one day grow to be the one force that could stop her reign of destruction.

Trained by her father to be the ultimate weapon, Cassandra was not taught to speak. Instead, the parts of her brain normally used for speech were trained so she could read other people's movements and body language and predict, with uncanny accuracy, their next move. This also caused her brain to develop learning functions different from most, a form of dyslexia that hampers her ability to read and write.

When she was 8 years old, Cain decided his experiment had progressed far enough for him to test Cassandra's abilities in the real world, and took her to a hit; the target being Faizul, a 'book man' in Macau. At the time Cassandra had no idea what she was doing and believed it was only a game (an interpretation in keeping with her own reaction to what happened, and matching the interpretation of Alfred Pennyworth, an expert on children who saw a tape of events). After striking a deathblow, she "read" the target as he died, and saw death as he saw it.

In addition to scarring her emotionally, she realized murder, like her father's profession, was wrong, and she ran away from her father.

Cassandra spent the next nine years homeless, beating herself up mentally over what she'd done as she traveled the world. Entering Gotham City at 17 Cassandra came to be one of Oracle's agents in the No Man's Land of Gotham City. After saving Commissioner Gordon's life from her assassin father, she was given the Batgirl costume with the approval of both Batman and Oracle. She became Barbara's ward and in a sense, the Batman's adoptive daughter. As the No Man's Land wore on the new Batgirl was introduced to the rest of the with varying levels of acceptance. Usually going out under the Batman's watchful eye she was finally allowed to go on a solo mission when a petrol station needed guarding against a local gang. Near the end of No Man's Land Batman noticed her death wish and forced her to make a decision between suicidal actions and self preservation. She opted for self preservation.

Despite her notable handicap of being unable to talk, read or write Cassandra did remarkably well. Capable of understanding others' intentions due to her ability to read body language she was a more than capable listener, even if she couldn't reply. It was this trait that made her one of the Batman's most loyal and trusted followers and helped her to survive when the became hunted by the Blood Hawks. Although the fact that she couldn't talk frustrated Barbara Gordon she proved herself useful in other ways during a team up with the spectral vigilante Ghost in hunting down disappearing corpses. The running successes and final understanding of her mission as Batgirl allowed Batman to give her the privilege of running solo in Gotham City on the condition that she faced no 'costumed criminals' (Joker, Bane, Two Face, Penguin, etc)

From going undercover in Madras with Batman to saving local heroes from the mob Cassandra continued to impress as the new Batgirl. Especially when, despite Batman's warnings, she went face to face with a meta-human and won. She even managed to, despite her restriction to Gotham City, make it on the reserve member list of Young Justice.

But Cassandra's career was not the only thing that was growing. In the background a rift between Oracle and Batman was slowly emerging, as was the growing image of Batman as a father figure in Cassandra's eyes but the major development was David Cain's growing longing to have his daughter back.

Batman learned about Cassandra's past when Cain transmitted a tape he had made of Faizul's death to the Batcave, but Batman nevertheless continued to accept Cassandra.

Things became more strained when a run-away psychic altered her mind so that she could understand words. As an after effect she lost her ability to read body language and thusly, her ability to fight. After she almost died while trying to protect the psychic from assassins Batman took away her costume and began retraining her. The training remained ineffective however, perhaps due to Cassandra's dwelling on her lost ability instead of focusing on accumulating more, and Cassandra wanted to roam the streets, with or without the costume. It was during one of these 'unauthorised' vigilante outings that she encountered her mother. Lady Shiva noted Cassandra's missing skills and offered to train in a way that will allow her to possess them again but in exchange they will fight in one year. A death duel. Cassandra accepted.

Cassandra began training immediately; going after every talented fighter she came across in order to gain more skills she even (after hearing about his notoriousity within the Bat-clan freed the Joker then apprehended him again in order to gauge just how good he was. Batman and Oracle deduced that Cassandra's death wish had not gone away and that it was due to guilt over her murdering Faizul. They began looking into what had brought the death wish back.

Her reckless training was interrupted when an Officer Down was called over the frequencies. Batman's longtime ally and friend, Commisioner Gordon had been shot in cold blood.

It was during yet another training session in the batcave that Cassandra first met her future friend Stephany Brown (The Spoiler).

It wasn't long until Batman gave her a cave of her own to operate from and her training crusade continued as she found even more powerful opponants like Bizzaro Supergirl and Shadow Thief during the Joker's Last Laugh as well as numerous female villians during the aftermath of Our Worlds at War. These activities had not gone unnoticed by Batman and Oracle but despite Oracle's protests Batman allowed Cassandra to continue until the fateful day arrived and Cassandra fought Shiva on the building tops of Gotham City. Shiva won the battle fairly easily, killing Cassandra with a shot to a nerve cluster near the heart but then, within a temple devoted to her, Shiva brought Cassandra back to life and requested another fight. This time, with her death wish satisfied, Cassandra Cain won and became the first to defeat Lady Shiva in martial combat. Unfortunately the victory would be short lived for Bruce Wayne was in jail, under suspicion of murder and Cassandra arrived back to the cave in time to see Batman leave.

It was during an investigation into the murder that Cassandra discovered that Batman and Bruce Wayne were in fact the same person. Later she, along with Spoiler and Nightwing discovered critical clues that pointed to Bruce Wayne's innocence and, eventaully, incriminating evidense to the real culprit; David Cain.

Her father safely behind bars and no battle-to-the-death with Shiva to train for Cassandra focused on her crime fighting career.

Batman regarded Cassandra very highly. During War Games, he relied heavily on her to help control the violence of the gang war in Gotham City.

Following War Games, Batgirl moved to Blüdhaven with Tim Drake at Batman's suggestion and with his financial support (Nightwing had been injured during the War Games, and the Gotham City Police Department had declared all costumed heroes illegal). There, she quickly made a name for herself by defeating the Society of Evil. Deathstroke later took on a contract from the Penguin to kill Batgirl and decided to let his daughter Rose Wilson (the current Ravager) do the job instead. Cassandra beat Rose by critically wounding her and giving Deathstroke no choice but to get her medical attention. It was during fathers' day that Cassandra became infatuated with knowing who her mother was. Interogating all the contacts she had (including Batman and her father, David Cain) she eventually found Lady Shiva.

Cassandra also went undercover in the Justice League Elite masquerading as an assassin named Kasumi. She revealed herself to Coldcast to tell him that he was not a bad person, right before he was accused of murder.

Cassandra has gained control over the League of Assassins. She recently encountered a shocked Robin and nearly killed him in battle. She also fought with Supergirl, during which time both combatants discovered that Supergirl possessed a bio-defense mechansim enabling her to generate Sunstone crystal from her body. Supergirl stabbed Batgirl through the shoulder with one of these crystal spikes. At this time, Batgirl also fell under the sway of Deathstroke who drugged her and used her as a tool in his revitalized Titans East team. Robin provided Cassandra with the antidote and she left the team and fought against Deathstroke.

Cassandra is also on the roster of Titans East and is once again wearing the Batgirl costume. Cassandra remained in the role of a villain, under the command of Titans East's leader, Deathstroke. It is revealed that she was being drugged by Deathstroke.

after a rematch with the Ravager and a brief confrontation with Robin, Robin injects a counter serum (prepared in case Deathstroke regains control of his daughter again) to Cassandra. She apparently regains control over herself, with a desire of revenge by killing Deathstroke for violating her like Ravager and Terra before her. Cassandra is allied with the Teen Titans (to which Miss Martian comments that she is more in control of herself now), and faces Slade, Match, and other former Titans East teammates, before being subdued by Risk. Soon after, Cyborg, Raven, and Duela Dent summon former Titans Nightwing, Donna Troy, Beast Boy, and Flash (Bart Allen), who joins in against Slade's team. Batgirl attempts to kill Deathstroke, but is stopped and knocked unconscious by Nightwing, who demands that Slade face the courts. Unfortunately, Deathstroke escapes from the Titans with the help of Inertia, and after the battle is over, Batgirl and Duela Dent both vanish without a word.

One-year Later Cassandra was left behind while Batman, Robin, and Nightwing left for their year long trip and Harvey Dent was charged with protecting Gotham instead of her. Deathstroke approaches Cassandra and preys on her desire for a loving father as well as her feelings of abandonment. Although shown off screen, Deathstroke managed to inject Cassandra with drugs from a distance, that warped her mind allowing for him to manipulate her to his liking.

Cassandra retakes the Batgirl mantle joining the Outsiders at Batman's request. Cassandra moves into their apartment but does not show much desire to socialize with her teammates. Batman also offers membership to Green Arrow, who is furious to learn that the former leader of the League of Assassins is on the team as well. While on a mission, Green Arrow and Batgirl battle one another, and end up gaining an unusual sort of respect for one another. The team as a whole begins to slowly accept Batgirl into their ranks, when she frees all of them from the Chinese military.

Cassandra moves into Wayne Manor and attempts to re assimilate with the Bat-family. However she continues with the desire to kill her father and Deathstroke for what they did to her. She uses the Batcomputer to locate them but is attacked by Nightwing, who claims she cannot be trusted. Robin and Batman give her the benefit of the doubt.

While searching for Cain's base, Cassandra discovers a mystery woman who is revealed to be Batgirl's half-sister, who rebelled against Cain. This half-sister had tried to kill Cain many times without success. They pool their resources together but are caught by Ravager. The three women agree to work together and continue the search for their fathers. They eventually find a training school run by Cain and Deathstroke that is filled with more of Cassandra's "sisters." During the fight that follows, they discover that Deathstroke has rigged the building to blow. Cassandra places listening devices at the school and learns that the intended use of the training school girls was to "cripple the meta-hero community," leading Cassandra to believe Oracle is the target of the plot.

Cassandra races to Platinum Heights, Oracle's new base of operations, and locates Cain on an opposite rooftop with a sniper rifle in his hand. Cassandra engages in one-on-one combat, breaking his hand and sending him over a ledge. Cain holds on for a few minutes before losing his grip. Cassandra attempts to save him and sees that he has only fallen to a ledge a few feet below, where he is detained by Batman, who had followed her to Platinum Heights. Because she tried to save Cain, Batman accepts her into his family again and states he will officially begin the process to adopt and make her his daughter.

Soon after Cassandra becomes Wayne's legal daughter, Batman disappears. As a result of his disappearance the Outsiders have been left in disarray with the loss of their leader. Batgirl, believing that Batman brought her in as a contingency, takes command of the team, while they attempt to locate Batman. During his absence, the rivalry that began between Nightwing and Batgirl reached its climax, leading to a fight between the pair. Alfred however arrived and broke up the argument, reminding them both that Gotham needed both of them to keep things together. Following this, Nightwing and Batgirl have at last appeared to have put aside their differences.

Unfortunately Batman was killed during his final confrontation with the new God, Darksied, thus leaving Dick Grayson, Cassandra Cain, Jason Todd and Tim Drake once again orphaned. Without Batman present, Batgirl leaves the Outsiders, who are taken over by Alfred. Batgirl however continues working with the Outsiders, along with a host of other heroes in protecting Gotham, which has exploded into chaos following the loss of Batman.

Azrael: Agent of the Bat #56 (September 1999): "The Night Foretold!"
Azrael: Agent of the Bat #57 (October 1999): "Scratched Out!"
Azrael: Agent of the Bat #60 (January 2000): "Evacuation"
Azrael: Agent of the Bat #61 (February 2000): "Presents of Mind"
Azrael: Agent of the Bat #66 (July 2000): "New Order"
Batgirl #1 (April 2000): [No Title]
Batgirl #1 (April 2000): [No Title] [Flashback]
Batgirl #10 (January 2001): [No Title]
Batgirl #11 (February 2001): [No Title]
Batgirl #12 (March 2001): "Mute Witness"
Batgirl #13 (April 2001): [No Title]
Batgirl #13 (April 2001): [No Title] [Flashback]
Batgirl #14 (May 2001): [No Title]
Batgirl #15 (June 2001): [No Title]
Batgirl #16 (July 2001): [No Title]
Batgirl #17 (August 2001): [No Title]
Batgirl #18 (September 2001): [No Title]
Batgirl #19 (October 2001): [No Title]
Batgirl #19 (October 2001): [No Title] [Flashback]
Batgirl #2 (May 2000): [No Title]
Batgirl #20 (November 2001): [No Title]
Batgirl #20 (November 2001): [No Title] [Flashback]
Batgirl #21 (December 2001): "Auto-Replay"
Batgirl #22 (January 2002): [No Title]
Batgirl #23 (February 2002): "Little Talk"
Batgirl #24 (March 2002): [Bruce Wayne: Murderer? Part Two] "Batgirl"
Batgirl #25 (April 2002): "I am Become Death, the Destroyer of Worlds"
Batgirl #26 (May 2002): [No Title]

Batgirl #27 (June 2002): [Bruce Wayne: Fugitive Part Five]
Batgirl #28 (July 2002): [No Title]
Batgirl #29 (August 2002): [Bruce Wayne: Fugitive Part Thirteen]
Batgirl #3 (June 2000): [No Title]
Batgirl #3 (June 2000): [No Title] [Flashback]
Batgirl #30 (September 2002): "Legion of the Lost"
Batgirl #31 (October 2002): "The Catafracts"
Batgirl #32 (November 2002): "Morituri"
Batgirl #33 (December 2002): "Father's Day"
Batgirl #34 (January 2003): "Lesson One"
Batgirl #35 (February 2003): "Blank Slate"
Batgirl #36 (March 2003): [No Title]
Batgirl #37 (April 2003): "Thicker Than Water"
Batgirl #37 (April 2003): "Thicker Than Water" [Flashback]
Batgirl #38 (May 2003): "Testline"
Batgirl #39 (June 2003): "Black Wind"
Batgirl #4 (July 2000): [No Title]
Batgirl #40 (July 2003): "Little Bat"
Batgirl #41 (August 2003): "Body Language"
Batgirl #42 (September 2003): "Death in a Bottle"
Batgirl #43 (October 2003): "Seeds of Blood"
Batgirl #44 (November 2003): "Harvest of Death"
Batgirl #45 (December 2003): "Soul"
Batgirl #46 (January 2004): "The Lost Girls"
Batgirl #47 (February 2004): "The Doll's House"
Batgirl #47 (February 2004): "The Doll's House" [Flashback]
Batgirl #48 (March 2004): "Human Resources"
Batgirl #49 (April 2004): "Down Among the Dead Men"

Batgirl #5 (August 2000): [No Title]
Batgirl #50 (May 2004): "Tough Love"
Batgirl #50 (May 2004): "Tough Love" [Flashback]
Batgirl #51 (June 2004): "The City is a Garden"
Batgirl #52 (July 2004): "The City is a Jungle"
Batgirl #53 (August 2004): "Sisterhood"
Batgirl #54 (September 2004): "Cooking the Books"
Batgirl #55 (October 2004): "War Games Act 1, Part 6: Total War"
Batgirl #56 (November 2004): "War Games Act 2, Part 6: Collateral Damage"
Batgirl #57 (December 2004): "War Games Act 3, Part 6: Ground Zero"
Batgirl #58 (January 2005): "Fresh Blood, Part 2: Following Footsteps"
Batgirl #58 (January 2005): "Fresh Blood, Part 2: Following Footsteps" [Flashback]
Batgirl #59 (February 2005): "Fresh Blood, Part 4: Settling Up"
Batgirl #6 (September 2000): [No Title]
Batgirl #60 (March 2005): "The Hood, Part One: Deep Digs"
Batgirl #61 (April 2005): "The Hood, Part Two: Into the Light"
Batgirl #62 (May 2005): "The Hood, Part Three: Dead Weight"
Batgirl #62 (May 2005): "The Hood, Part Three: Dead Weight" [Flashback]
Batgirl #63 (June 2005): "Could've Been, Part One: Nowadays"
Batgirl #63 (June 2005): "Could've Been, Part One: Nowadays" [Flashback]
Batgirl #64 (July 2005): "Could've Been, Part Two: Gone, Daddy, Gone"
Batgirl #64 (July 2005): "Could've Been, Part Two: Gone, Daddy, Gone" [Flashback]
Batgirl #65 (August 2005): "A Mother of A Father's Day"
Batgirl #66 (September 2005): "Destruction's Daughter, Part 1: Hitting Pavement"
Batgirl #67 (October 2005): "Destruction's Daughter Part 2: Bird Calls"
Batgirl #67 (October 2005): "Destruction's Daughter Part 2: Bird Calls" [Flashback]
Batgirl #68 (November 2005): "Destruction's Daughter Part 3: Motherlode"
Batgirl #69 (December 2005): "Destruction's Daughter Part 4: Love's Labors..."

Batgirl #7 (October 2000): [No Title] Batgirl #7 (October 2000): [No Title] [Flashback] Batgirl #70 (January 2006): "Destruction's Daughter Conclusion: The Resurrection and the Life"
Batgirl #71 (February 2006): "Blood Matters, Part One: Prey for Her"
Batgirl #71 (February 2006): "Blood Matters, Part One: Prey for Her" [Flashback]
Batgirl #72 (March 2006): "Blood Matters, Part Two: Turning Abel"
Batgirl #73 (April 2006): "Blood Matters, Conclusion: Revelations"
Batgirl #73 (April 2006): "Blood Matters, Conclusion: Revelations" [Flashback]
Batgirl #8 (November 2000): [No Title]
Batgirl #9 (December 2000): [No Title]
Batgirl #9 (December 2000): [No Title] [Flashback]
Batgirl Annual #1 (August 2000): [No Title]
Batgirl Vol. 2 #1 (September 2008): "Redemption Road, Chapter One: Square One"
Batgirl Vol. 2 #2 (October 2008): "Redemption Road, Chapter Two: Trust is a Ghost"
Batgirl Vol. 2 #3 (November 2008): "Redemption Road, Chapter Three: Daughters"
Batgirl Vol. 2 #4 (December 2008): "Redemption Road, Chapter Four: Daddy Issues"
Batgirl Vol. 2 #5 (January 2009): "Redemption Road, Chapter Five: As My Father Made Me"
Batgirl Vol. 2 #6 (February 2009): "Redemption Road, Chapter Six: The Great Gray Dragon"
Batman #567 (July 1999): "Mark of Cain, Part 1"
Batman #569 (September 1999): "I Cover the Waterfront"
Batman #594 (October 2001): "Sanctuary, Part Two"
Batman #600 (April 2002): [Bruce Wayne: Fugitive Part One] "The Scene of the Crime"
Batman #605 (September 2002): [Bruce Wayne: Fugitive Part Eighteen] "Courage"
Batman #631 (October 2004): "War Games Act 1, Part 8: Last Stand at Alamo High"
Batman #632 (November 2004): "War Games Act 2, Part 8: Orpheus in the Underworld"
Batman #633 (December 2004): "War Games Act 3, Part 8: No Going Back"
Batman and the Outsiders Vol. 2 #10 (October 2008): "Monsters"
Batman and the Outsiders Vol. 2 #11 (November 2008): "Outsiders No More, Part 1 of 2"

Batman and the Outsiders Vol. 2 #12 (December 2008): "Outsiders No More, Part 2 of 2"
Batman and the Outsiders Vol. 2 #13 (January 2009): "The Network"
Batman and the Outsiders Vol. 2 #14 (February 2009): "A Family Affair"
Batman and the Outsiders Vol. 2 #2 (January 2008): "Infestation"
Batman and the Outsiders Vol. 2 #3 (February 2008): "Throwdown"
Batman and the Outsiders Vol. 2 #4 (April 2008): "Mission: Creep"
Batman and the Outsiders Vol. 2 #5 (May 2008): "Ghosts"
Batman and the Outsiders Vol. 2 #6 (June 2008): "Ghost Star"
Batman and the Outsiders Vol. 2 #7 (July 2008): "The Snare"
Batman and the Outsiders Vol. 2 #8 (August 2008): "The Hard Way"
Batman and the Outsiders Vol. 2 #9 (September 2008): "The Uninvited"
Batman Chronicles #18 (Autumn 1999): "Spiritual Currency"
Batman: Family #6 (February 2003): "Machinery"
Batman: Family #7 (February 2003): "Precipice"
Batman: Family #8 (February 2003): "Blackout"
Batman: Gotham City Secret Files #1 (April 2000): "Night Games"
Batman: Gotham Knights #2 (April 2000): "Down With the Ship"
Batman: Gotham Knights #5 (July 2000): "Locked"
Batman: Gotham Knights #56 (October 2004): "War Games Act 1, Part 4: Rules of Engagement"
Batman: Gotham Knights #57 (November 2004): "War Games Act 2, Part 4: The Light at the End of the Tunnel"
Batman: Legends of the Dark Knight #120 (August 1999): "Assembly"
Batman: Legends of the Dark Knight #124 (December 1999): "Captain of Industry"
Batman: Legends of the Dark Knight #182 (October 2004): "War Games Act 1, Part 2: Behind Enemy Lines"
Batman: Legends of the Dark Knight #183 (November 2004): "War Games Act 2, Part 2: Philosophical Differences"
Batman: Legends of the Dark Knight #184 (December 2004): "War Games Act 3 Part 2: The Road to Hell"
Batman: Orpheus Rising #3 (December 2001): [No Title]
Batman: Orpheus Rising #5 (February 2002): [No Title]
Batman: Shadow of the Bat #93 (January 2000): "Assembly Redux"

Birds of Prey #27 (March 2001): "Officer Down, Part Three: Armed and Dangerous"
Catwoman Vol. 2 #90 (March 2001): "Officer Down, Part Four: Smoking Gun"
DC First: Batgirl/Joker #1 (July 2002): "Clowntime"
Detective Comics #734 (July 1999): "Mark of Cain, Part 2"
Detective Comics #738 (November 1999): "Going Downtown, Part Two: The Vandal"
Detective Comics #739 (November 1999): "Jurisprudence, Part II"
Detective Comics #790 (March 2004): "Scarification"
Detective Comics #797 (October 2004): "War Games Act 1, Part 1: Flashpoint"
Detective Comics #799 (December 2004): "War Games Act 3, Part 1: Good Intentions"
JLA #88 (early December 2003): "Trial by Fire, Part 5"
Joker: Last Laugh #3 (December 2001): "Lunatic Fringe"
Nightwing Vol. 2 #98 (December 2004): "War Games Act 3, Part 3: Casualty of War"
Robin Vol. 2 #133 (February 2005): "Fresh Blood Part Three: The Auction"
Robin Vol. 2 #148 (May 2006): "Robin, Boy Wanted - One: Out Go the Lights"
Robin Vol. 2 #149 (June 2006): "Assault On Precinct Nine"
Robin Vol. 2 #150 (July 2006): "Hard Answers"
Robin Vol. 2 #151 (August 2006): "Harder Questions"
Robin Vol. 2 #70 (November 1999): "War Beneath the Streets Part Three"
Robin Vol. 2 #73 (February 2000): "The World Around the Corner"
Robin Vol. 2 #86 (March 2001): "Officer Down, Part Two: Behind the Lines"
Robin Vol. 2 #88 (May 2001): "Secrets & Lies"
Robin Vol. 2 #98 (March 2002): [Bruce Wayne: Murderer? Part Six] "The Thin Line"
Superboy Vol. 3 #85 (April 2001): "Silent, But Deadly"
Superman/Batman #5 (February 2004): "The World's Finest Part Five: State of Siege"
World War III #1 (June 2007): "A Call to Arms"
World War III #2 (June 2007): "The Valiant"
World War III #4 (June 2007): "United We Stand"
Young Justice #21 (July 2000): "Young, Just Us Too"