Titan

Titan is a compound created by Dr. Penelope Young and used by the Joker using research on Bane and the drug used to give Bane his super-strength, venom. Like venom, Titan can turn any user of it into a Bane-like monster, however they lose their sanity and act like hulking beasts. However, as an example from the Joker is that anyone who is already insane still has their intelligence.

Batman: Arkham Asylum
Joker plans to use this compound to create an army of Bane-like monsters and take over Gotham City, and also with the rest of the world with it. He planned to flush the chemical in the city's water supply, which would turn anyone who used it into giant, hulking monsters.

It is revealed by Poison Ivy that there is an antidote for Titan, which are strange plant spores from Killer Croc's lair. Batman was able to find some spores and liquefy them to make an antidote.

There is also people who can resist the effects of Titan, as demonstrated by Batman when Joker injected him with a Titan dart. However, the resistance could not lost long as Batman was about to transform any minute, so he used the only antidote on himself.

Titan has different effects on super-powered people. When Poison Ivy was injected with Titan by the Joker, Ivy's plants got stronger and they tried to overtake the island while Ivy herself did not undergo a monstrous transformation.

Despite the fact that there is an antidote for Titan, the toxin's effects wear off, but render the previous user to an ill stasis.

Though all the Titan was thought to be destroyed, a post-credits scene revealed that one box was left floating in the water, and three alternate endings showed either Bane, Scarecrow, or Killer Croc grabbing the crate.

Users

 * The Joker
 * Poison Ivy
 * Various Members of the Joker's Gang
 * Various Arkham Staff
 * Venom Henchman
 * Bane (possibly)