Cain is notoriously known as one of the worlds most dangerous and lethal assassins, it is because of this it is no surprise that such a deadly man would be a member of the
One of the things that had made Cain such a dangerous person was his careful planing and preparation for the future. This caused Cain to seek an apprentice to train and become his eventual successor. Cain introduced the idea to the leader of the League of Assassins who was
Ra's agreed with Cain's plan as Ra's wanted the apprentice that Cain would train to be a body guard for him.
Cain then put his plans into action training children while they were young to be deadly assassins but most of them failed and the aftermath of Cain's project was a child who was named Mad Dog for his similar attitude to the creature. Cain saw the Mad dog as a deadly assassin but with very little intelligence so decided to try again but with a different method this time.
Cain thought the best way would be by having a child of his own to train who would potentially inherit Cain's skill. This led David Cain to Sandra wu-San who also had high fighting abilities.
Cain saw Sandra's potential and the fact that she was being held back by her sister. To unleash the potential the Sandra had, Cain killed Sandra's sister which led Sandra to pursue and battle Cain. Sandra lost the fight to Cain but learned of her true fighting potential and decided to better her self. Cain agreed to train Sandra under the condition that she be the one to bear his child and that when the child would be born Sandra would give the child to Cain to be trained. Sandra who wanted to travel the world to better her abilities agreed to the deal. With this Sandra San agreed to definitely be the mother to Cain's child who he would train to be as a deadly as he is if not deadlier. Sandra would then go on to train with Ras and later become who is now known as Lady Shiva
one of the deadliest fighters in the world.
The progeny of this mating was a beautiful dark haired girl who he named Cassandra
after her mother. Cain trained and focused the child, teaching her martial arts, weapon control and body techniques. He focused her on physical skills and refused to empower her mind with the ability to speak or write. Using all her focus to learn the power of mimicking the other person she fought, using the body language as her skill. Training her among the League of Assassins
he worked hard to make her the greatest fighter.
At a young age Cain took Cassandra to an assassination and forced her to kill someone. Frightened by her actions Cassandra fled from him. Living on the streets she was eventually adopted into the Bat Family
much to her fathers dishonour.
During a mission David Cain and Deathstroke
are both hired for the two interact and fight, each finding a mutual appreciation for the others skill. Also sharing a history with the League of Assassins
, the two team up too help build a new army of girls. Though neither trusts the other, their shared skill and lore bind them as well as their love of their tortured children.
Cain is approached by Lex Luthor
and hired to kill Vesper Fairchild
and frame Bruce Wayne
for the murder. Cain takes the job to watch Bruce and see if he is the right person to take over the care of his child Cassandra. Cain and Batman fight at the end of the story arc and it is here that he sees the Bruce is indeed the right man to raise his daughter, that his fighting abilities and his desire to make the world better could perhaps protect his only daughter. Realising this Cain allows himself to be captured to prove that he was the murderer not Bruce, thus clearing Batman of the charges.
During his time in prison Lex afraid that he will come forth and implicate him in the murder sends Deadshot to kill Cain in prison. Cain at first allows Deadshot
to take him down with all hope lost to him he begins to think of his daughter and fights back, killing Deadshot. Not long afterwards Cassie visits him in prison fighting him she begs to know her mothers name, even though Cain refuses to give it to her she vows to kill him if they meet again. He then escapes from Prison not long after. He ventured out to capture Cassandra.
One Year Later
Cain and Deathstroke
worked together to inject Cassandra with the serum and use the mind altering substance to force her to become the new leader of the League of Assassins.
as a device, Cain plots to protect Cassandra from becoming Batgirl again and allows her to think she has killed him. Not long after he flees with her away from Robin and back into the League. Cassandra manages to break free of their hold over her when Robin injects her with a counter active serum that he carries for Ravager
if her father Deathstroke ever uses the same substance on her again. Cassandra vows to hunt down her father and kill him for destroying so many girls lives, once it has been revealed that he and Slade have formed an army of metahuman
girls to use as weapons
During the Batgirl series, Cain finds his daughter and her friends about to attack the compound where he and Deathstroke are training the new breed of Metahuman girls. Attacking the girls he eventually blows up the compound realising it is the only way too protect their interest and keep Batgirl and the other two off the scent of their plan. While dealing with an angered Deathstroke Cain is overheard by Cassandra using a new equipment picked up by Batman. During the conversation Cain speaks of their ultimate plan to "cripple the metahuman community". When Cassandra realises his plan is to kill Oracle he is intercepted by her at the last moment.
Fighting with his daughter he tries to convince her yet again to come back to him and for them to work together, That he truly loves her and wants the best from her. Cassie is finally able to break the bond and attacks, as they fight he falls of the building and clings from the edge. Cassandra battles with her desire to kill the man who has caused her so much pain but forces through it just as Batman and Robin appear to help. She tries to stop Cain from falling but he lands on a small ledge below and is safe.