Venom is a highly-addictive super-soldier serum/compound engineered to greatly increase one's physical attributes. It is notably used by Bane. More powerful versions of Venom were developed in the form of TN-1 and Titan.
Before Arkham Origins Incident
Venom was originally developed in the Caribbean island nation of Santa Prisca to create an army of super-soldiers. It was decided that the residents of the hellish prison of Peña Duro would be used as human guinea pigs for Venom. However, none of the prisoners that were put through the Venom process were strong enough to survive the procedure.
At the same time, Bane, a prisoner who had grown up in Peña Duro, had trained his body and mind to perfection while surviving his violent surroundings, ultimately established himself as the "king" of the prison. Peña Duro's officials took note and, eventually, forced Bane to become a test subject for Venom. It nearly killed him at first, but Bane's physical hardiness and unbreakable resolve enabled him to survive the process. Bane found that Venom enhanced his physical attributes, and multiplied his strength and stamina to super-human levels. Sometime later, Bane used his new strength to escape Peña Duro and made his way to Gotham City.
Arkham Origins Incident
After Black Mask placed a bounty on the vigilante known as Batman, Bane was among the assassins that were assigned to take the Dark Knight down. After a couple failed attempts to take him down, Bane replaced his regular Venom supply with an enhanced version known as TN-1.
Arkham Knight Incident
Bane eventually left Gotham City and started fighting his Venom/Titan addiction. After long months of painful withdrawal, he returned to Santa Prisca to look for a new start. But upon returning to his homeland, Bane observed that his country was embroiled in a bloody turf war between the various cartels and drug lords (amped up on Venom), who had killed countless innocent lives including children. Bane decided to renew his war on Venom and all who supplied it. He eventually ended up killing the country's twelve most powerful drug lords and lined up their decapitated heads on the beach.
- Bane apparently needed to have regular doses of Venom or else his body withered away as shown in Batman: Arkham Origins Blackgate and briefly in Batman: Arkham Asylum. That could be why Bane was "addicted" to Venom in the Arkhamverse.
- In the original comics (and conceivably in the backstory of the Arkhamverse), just as Dr. Penelope Young developed Titan from Venom, so did an amoral scientist named Randolph Porter develop the first batches of Venom, that was used as part of a scheme to control Batman, from an older drug named Miraclo, used by a Golden Age 'Mystery Man' named Hourman, secretly the head of a pharmaceutical company. Ultimately, that proved addictive to both the elder hero and later his son. It also started a tragic pipeline that haunted the heroes of the DC Multiverse in all timelines.
- TN-1: A stronger Venom prototype that was developed around the time of the Christmas Eve Incident.
- Titan: A super powerful, lethal version of Venom that was produced by Dr. Young around the time of Batman: Arkham Asylum.