Batman

When his parents were gunned down in front of him, young Bruce Wayne resolved to rid Gotham City of the criminal element that took their lives. He trained extensively to achieve mental and physical perfection, in addition to mastering martial arts, detective techniques, and criminal psychology. Dressing as a bat to prey on criminals' fears, Batman fights crimes with the aid of specialized gadgets and vehicles, operating out of his secret Batcave below Wayne Manor. In addition to this, he had a secret batcave hidden under Arkham Asylum, unknown to all but him.

Road to Arkham
After the escape of the Joker from Arkham Asylum two months prior, Batman had been on a constant search for the clown prince of crime. During his second month of searching, Batman was notified of an anonymous tip left in Dr. Sarah Cassidy's office at Arkham which revealed that she had been kidnapped by Zsasz and taken to the Old County Hospital. He took Zsasz out by surprise and rescued Cassidy from his clutches. In the same month, a second tip came in the form of a note attached to a test tube. Unsurprisingly to Batman, the vial contained an extremely potent, odorless fear gas.

Whilst experimenting with it in the Batcave, a few molecules escaped from the vial causing Batman to fight his way out of a series of fear induced hallucinations. Batman was able to create an antidote from the formula and ambushed the Scarecrow, attacking his psychologist, taking him back to his cell and curing his victims. The GCPD received the third and final tip in the form of a 911 call, moments before the Joker raided Gotham City Hall and took the Mayor hostage.

The Joker strapped the Mayor to the side of a large pillar on the roof of the building, attaching a bomb to his waist. Batman destroyed the Joker's detonator and removed the bomb before it exploded. The Joker attempted to escape via parachute but Batman easily thwarted the villain. Whilst escorting the Joker back to Arkham, he spoke with Oracle via radio, vocalizing his suspicions on the three tips and whether they came from the same source, as well as the easy nature of the Joker's capture. Despite these suspicions he drove the Joker back to Arkham, hoping they would disappear once he was back behind bars.

Batman: Arkham Asylum
Batman arrived at Arkham in the Batmobile, taking the Joker to the Intensive Care Facility. The Joker remained in high spirits, pleased that he was back in Arkham. He was strapped to a prisoner movement trolly and wheeled through Intensive Care by a variety of security guards, including Frank Boles, with Batman following close by due to Batman sensing something amiss about his capturing Joker and returning him to Arkham, as the Joker never let him capture him this easily before.

The Joker commented on all the brand new security at Arkham and how it was rather funny that a fire at Blackgate Penitentiary sent over a hundred of his goons to Arkham (To which Frank Boles reacted angrily and reminded Joker that he was supposed to keep quiet about it, before Joker implied that Bole's mouth should remain quiet for his own good). During the escort, the Joker made snide remarks to many of the Arkham Staff including Warden Quincy Sharp, Officer Aaron Cash and Dr. Penelope Young before being taken down the elevator. In addition, when scanning the Joker for carrying weapons, the scanners also inadvertently detected multiple prohibited weapons on Batman.

During the elevator journey, a blackout occurred causing the Joker to laugh hysterically before having his neck clutched by Batman as the lights turned back on. As the Joker was moved into the lobby area, he was unstrapped and escorted by a guard and an orderly while Batman and Commissioner Gordon looked on. Unbeknown to all but Joker, Harley Quinn was already in the security control room, waiting. Joker soon took the opportunity to break free as Harley's signal.

Pretending to stumble and trip, the Joker bashed his guard in the face with the back of his head as the guard demanded him to get up. He then used his handcuffs to strangle the guard, forcing the doctor to unhook the Joker to save the guard. Joker strangled the guard to death before the doctor could save him, and when his cuffs were finally off, kicked the doctor down, killing him as well.

The Joker then coldly said to the dead guard "The choke's on you!", imitated a playful laugh, and pointed at the security door with a "Ta-da!". He looked up at the security camera and told Harley he was home. She then let him in by opening up the adjacent electrical doorway, allowing the Joker to access the cell controls. He ran behind the energy screen just as Batman managed to break through the viewing window and into the room. He taunted the Dark Knight for springing his trap and released his followers from Blackgate out of their cells, saying "Now let's get this party started!". As Batman battled the thugs, Joker said over the monitor system that he was originally going to kill everyone in the room and watch cartoons, but decided to take a captive audience instead. After Batman defeated a round of thugs, the Joker left the room and made his way to the patient transfer unit.

Batman told Gordon he would find them a way out, but Joker told Batman not to make promises he couldn't keep, as he was in control of the asylum and therefore where Batman was able to go. As Batman told Joker he wouldn't let him run, Joker cut off his "hero speak" and goaded him to just pursue him. Batman followed the Joker through the depths of the Intensive Treatment Facility, finding deceased Arkham security guards in his wake of destruction. Batman halted briefly to defuse a hostage situation in the Patient Pacification Chamber, where an escaped Victor Zsasz had taken a security guard, Mike, hostage and had strapped him into the electroshock pacification chair.

Batman then eventually followed Joker's trail of smiles and arrows drawn by spray paint and dead bodies and found the villain in the Secure Treatment Transfer area. The Joker opened up a large patient transfer cell, releasing a large experimental monster. The monster attacked Batman before dying of biological causes, much to the Joker's annoyance, who murmured "Note to self: Need stronger test subjects!". As a result, the Joker allowed Batman one free shot at him, which would cause him to fall to his death and end the madness. Batman drew a Batarang, but hesitated and was unable to willingly kill his enemy, causing the Joker laugh at him and say that he was becoming "too predictable".

He escaped via the patient transfer system and told Batman that he was organizing a "party" with the villains all over Arkham. Whilst Batman tried to get the transfer unit working again, the Joker appeared on a monitor showing Batman an image of a treacherous Frank Boles knocking out Gordon and taking him hostage, ready to kill him should Batman follow.

He claimed that he helped Boles out of a situation a while back in which Boles owed him. Batman attempted to track down Gordon anyway, by detecting the alcohol Boles left in the air. Along the way, Joker left traps with Joker Venom as well as many gag chattering teeth. The Joker soon caught onto the Batman's attempt and as a result had Boles killed, no longer needing him.

The Joker took control of Arkham's intercom system, telling his goons to destroy the Batmobile as he took over the West side of Arkham Island. His next target was the Medical Facility where he ordered his goons to round up all the doctors in the area, most importantly Penelope Young, who he needed the Titan formula from.

To the Joker's annoyance, Batman defeated his goons and rescued the captive doctors. The Joker drew up a 'party list' which contained the individuals who would help take care of Batman. He enlisted the help of the Scarecrow, who proceeded to attack Batman in the Medical Facility. After escaping Scarecrow's Fear Toxin hallucination, Batman made his way to Gordon, who was conveniently placed near Bane's holding cell.

After Batman rescued Gordon from Harley, the Joker pumped a large amount of Titan into Bane, causing a fight with him and Batman. Joker was disappointed with Bane's inability to kill Batman, so he ordered his goons to assist him, though Batman defeated them all. The Joker's next order of business was to search Arkham Mansion for Dr. Young's formula, and Dr. Young herself, who had gone looking for said formula. After finding Zsasz in the Botanical Gardens, the Joker enlisted his help to deal with Dr. Young. Zsasz held Young by a knife in Warden Sharp's office and threatened to kill her if he saw Batman approaching.

Joker told Zsasz to just kill her, as she was useless to him since he had gotten both Venom and Titan anyway. Batman incapacitated Zsasz and rescued the doctor, though an explosion set by Joker in the Warden's safe killed Young anyway. Harley then entered and had her thugs prepare Batman for the 'party'. He defeated them and followed Harley, rescuing Sharp by tracking his DNA. Harley was shown releasing Poison Ivy from her cell, despite Ivy not being on the 'party list', much to Joker's apparent pleasure. He then unleashed the more violent, insane inmates all over the island.

Batman went after Harley Quinn, who sent her thugs after Batman again, though he managed to defeat them all. Harley's failure prompted Joker to remove her from the 'party list', and Batman defeated and locked her up, using her DNA traces from around the island to track Joker to the Botanical Gardens, where he found the Joker forcing him to play a deadly game in the aviary: He strung a pair of orderlies, Luke Curtis and Robert Stirling, in birdcages over a deadly chasm and was challenging Batman to rescue them as his men patrolled the area.

Batman was successful in taking down the cage operator while dodging the other henchman. The threat removed, Batman rescued the two orderlies, who informed him of a secret entrance to the Titan Production Facility. Once there, Batman watched as The Joker demonstrated the successful Titan strain he had managed to create by injecting two of his thugs and having them attack Batman before escaping. The beasts attempted to hit Batman with their huge hands and resorted to hurling at him the corpses of deceased Arkham security guards that littered the area.

Batman defeated the monsters and pursued Joker, passing the bodies of Robert Stirling and Luke Curtis on his way back through the gardens. Batman swore to avenge their deaths ("They're all dead. Joker was busy while I fought his monsters. He will pay for this."). As Batman continued in his pursuit of the Joker, the villain revealed over the intercom that he had teamed up with Poison Ivy and injected her with Titan, causing her to become far more powerful and take control of the island surface with her evolved plants.

Batman defeated Scarecrow and Killer Croc down in the sewers and successfully harvested the spores needed to make an antidote for the Titan injection in Croc's lair. Batman then went down further into the sewers and found that Joker was trying to pump Titan pollutants into Gotham, telling his men to stop Batman from preventing this in a threatening, serious manner. After Batman shut off the pumps, Joker sent a Titan monster as a token of his disapproval.

Batman defeated the monster and escaped the sewers. Driven by more power hunger, Ivy betrayed Joker and swore to go after him once Batman was killed. Joker assured her that he would be prepared for her with an army of Titan monsters, saying the she could "bring the wine" and he would "make the salad". Batman managed to defeat Ivy in the gardens. With all of the enemies on Joker's 'party list' defeated, Joker had his men set off several fire works directing Batman, the 'guest of honor', to the 'party' at the Visitor Center by the Cell Block.

Rather than fight Batman, upon his arrival and confirmation of being on the 'guest list', the goons acted friendly, cheered him and allowed him safe passage. Batman found a bomb planted by Joker in the visitor center and upon its explosion, discovered the Joker's lair, a throne room atop various plastic toys from which he had been broadcasting to the island. Joker was holding Scarface the puppet and taking out his frustration on him by having a fictional argument before throwing him away. He then sent two more Titan powered thugs at Batman, who defeated them.

Joker then revealed that he had recaptured Gordon. Firing a Titan strain at Gordon, Joker was overjoyed when Batman took the shot himself. However, he was angered when Batman resisted and fought off Joker's attempts to make him give in. Joker then claimed that he had nothing to live for, as Batman would not allow him victory, and shot himself in the neck with the Titan injection gun, comically acting as if he was committing suicide.

He quickly awoke and mutated into the most horrific Titan monster, while still retaining his regular intelligence due to already being insane. He then directed the circling Gotham News helicopters and Jack Ryder to the rooftops of Arkham so that they could watch his final fight with Batman. Strapping Gordon to an electric chair above a makeshift fighting arena (making him the "referee"), the mutated Joker goaded Batman to give into his injection, as it was the only way they could be on even fighting terms. Batman refused and used the only antidote injection on himself, which the Joker found hilarious. The two, with assistance from Joker's henchmen, then fought a brutal battle, with Batman knocking Joker into the electrical generator used to torture Gordon.

The Joker got up from the attack and said he could take anything Batman threw at him, and asked if the Dark Knight was ready for the next round. Spraying Explosive Gel onto his glove, Batman declared that he would never let Joker win and would always be prepared for his tactics. Enraged, Joker prepared to kill his relentless nemesis as Batman charged him.

The gel on Batman's fist fiercely knocked Joker down as he was punched in the face. The GCPD then retook control of Arkham Island, imprisoned all of the inmates back in their cells, and watched over the Titan injected thugs as they returned to normal. Joker's transformation back to humanity was quite painful compared to others, culminating with the severe injuries he received in his battle with Batman. He was then securely locked back up, his plans having ultimately failed.

Outside the Centre, Gordon tells Batman that the effects of Titan are starting to wear off the Joker and his men, and that they are being taken back to their cells. Batman is informed that Two-Face is raiding The Second National Bank of Gotham, and flies away into the night in the Batwing to the scene of the crime.