Titan

Titan is a compound created by Dr. Penelope Young and used by the Joker using research on Bane, specifically the drug used to give Bane his super-strength, Venom, and Poison Ivy's plants. Like Venom, Titan can turn any user of it into a Bane-like monster, but only a small amount is needed to trigger the transformation due to its potency, removing the need for a storage device. Though it comes at a heavy price for most; their rationality is lost and those infected attack anything unlike them. Bane, due to his previous use of Venom, is able to stay "sane" and the Joker as well due to already being insane.

Batman: Arkham Asylum
Titan was originally conceived by Dr. Young as a way for weaker patients to survive more strenuous treatments, and funded by the Joker under the Alias Jack White to create an army "of a thousand Banes". Dr. Young's patient records implies that the Scarecrow assisted in the creation of the formula.

Venom was drained from Bane's body against his will to research Titan, plus the use of Poison Ivy's plants. The resulting compound bore little resemblance to the original Venom formula and was extremely potent. The effects of Titan typically grows the subject into a musclebound berserk superhuman, with increased strength, speed, and more resistant to melee attacks. The rapid transformation causes tears to the skin and bones to protrude out of the skin. It appears that all of Joker's Titan-enhanced henchmen were even more aggressive than they would normally be for a Blackgate convict, and behaved like raging beasts. Joker appears to not suffer this side effect, and even retains his speech and normal behaviours. The effects of Titan on Poison Ivy, though, are very different, most likely because she is not fully human anymore. Instead of undergoing a transformation into a giant killer plant, it is her plants that experience rapid growth, and their attacks becoming more powerful. Ivy's eyes turned bright glowing green and her chlorokinetic abilities were enhanced.

On interrogating Ivy, Batman discovers that special plant spores in Killer Croc 's lair were key to creating an antidote. Batman described the process for the synthesis of the antidote as slow, and only yields small quantities. Although Batman had set his computer to synthesise more, the untimely growth of Ivy's Titan-enhanced plants invaded the Batcave and destroyed the computer, leaving Batman with very little antidote.

Fortunately, the effects of Titan was still only temporary, transformed inmates eventually returned to normal. The Joker, however, would suffer worse due to residual Titan interacting with other chemicals in his bloodstream due to an overdoese from his dart gun.

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 (based on the completion rate of the game).

After Arkham
During the comic book series bridging the gap between the two games, it's revealed that the Titan mixture has made its way into the Gotham underground. Crates of the stuff floated into the docks and Two-Face bought it off of some gang bangers hoping for quick cash. Little late did he realize the mistake of having Brother-Sister team T&T (whose real names are Terry and Tracy Trask) take them down into a cellar.

Upon discovering what it was, they started using it and turned the cellar into a personal training ground. Because they used the drug in small controlled doses, they're able to retain control of themselves, and after slaughtering Two-Face's gang and nearly putting the man himself into a full body cast, T&T started making plans to take over the city.

However it's soon revealed that T&T were actually under the employment of Hugo Strange and under his instructions launched a coup against the city. Unfortunately for them, Batman arrived in time to save the city, but before he could trace them back to Hugo Strange they vaporized themselves via high explosives planted in their bodies, killing hundreds.

It's made clear that the purpose of the attack was to give Mayor Quincy Sharp the excuse he needed to create Arkham City. It seems that the Joker is planning to use the Titan again having had a doctor, which he promptly sent into a incinerator, isolate the Titan from his blood. In addition, the Joker had some of the Titan formula that was isolated from his blood injected into one of his henchmen, and then sent him after Bane.

After the henchman managed to place Bane at his mercy, however, the henchman started to suffer from cardiac arrest, resulting in Bane having to mercy kill the henchman. Due to this experience, Bane also vowed to destroy the source of all Titan by any means necessary.

Batman: Arkham City
After Bane's encounter with Joker's thug he launched a crusade against the Titan drug, realizing that he can't do it alone he signaled Batman with a flare and lured him into the abandoned Krank Co. Toy Factory in the flooded section of Arkham City. There he alerted Batman to the Titan in Arkham City (Depending on what point in the game the player chooses to meet Bane Batman will either find out from Bane or know of the Titan from a run in with the Penguin). According to Bane, the Joker was the one who arranged for the Titan crates to come into Arkham City.

Bane states that each of the remaining 12 Crates have been given a radio tracking device, Batman will destroy the six dotted around the south of Arkham City and Bane will take the northern six. Once Batman destroys his six he meets up with Bane and are ambushed by TYGER thugs. Batman and Bane quickly defeated them. Bane then reveals that his intent was to hoard the Titan to use for his own purposes.

Batman, however, anticipated Bane's betrayal. He was counting on Bane to hoard the containers and store them all in one place, so that they would be all that easier to destroy. Batman trapped Bane, then destroys the Titan canisters, finally ridding Gotham of the Titan.

Meanwhile, Joker used the isolated strain of Titan as a barganing chip, having medical blood filled with the poison sent all over Gotham and injected into Batman.

The Titan, having been altered due to exposure to the other chemicals in Joker's bloodstream, would kill people in 24 hours. Batman had to rescue Mister Freeze from Penguin to make the cure. However, Freeze needed a specific enzyme to render the cure stable, which so happens exists in the blood of Ra's al Ghul due to his longevity. Batman infiltrated the League of Assassin's base, and forcefully took Ra's' blood.

Freeze was able to create the cure, but decided to hold on to it in exchange for his wife, Nora. He and Batman got into a fight over the cure, and while they were fighting, Harley Quinn stole the cure. The cure was in turn stolen from Harley by Talia al Ghul. The Joker killed her for it and the cure wound up in the hands of Clayface. Batman defeated Clayface and took the cure, he sipped it and cured himself before Joker stabbed him in the arm, causing Batman to drop the vial on the floor. Joker died as a result from Titan poisoning.

Users

 * The Joker
 * Poison Ivy
 * Batman (resisted the change)
 * Various Members of the Joker's and Penguin's Gang
 * Various Arkham Staff
 * Titan Henchman
 * Bane (Forced by Joker)
 * T&T

Trivia

 * A similar concoction called Kobra-Venom appeared in Young Justice, which resualted in a permenant transformation by mixing Venom with the Blockbuster formula.