Venom is a highly addictive super-steroid. It was originally based on the Hourman’s Miraclo formula although it does not have the same 60 minute limitation as Miraclo. The drug, usually injected in a constant supply into the base of the neck would instantly transform someone into a hulking mass of unbridled physical strength. Bane's apparatus included a special "boost" button to give him a jolt of Venom when needed.
However, as the drug wore off or when the user was cut off from its constant supply, their body would rapidly return to its original state or sometimes even weaker, at which point the user would suffer from massive, debilitating withdrawal, usually accompanied by terrifying hallucinations.
Batman became addicted to the drug while searching for a way to cope for his physical limitations and imperfections, forcing him to eventually lock himself in the Batcave to "detox" himself when he realized how dependent on it he had become. Later, it resurfaced as the power source for Bane, who used it to overpower and cripple Batman by breaking his back over his knee.
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