poisonous blood: The Joker's physiology is all wrong. It was altered the day he fell into the chemicals and the fact that he tests his weapons on himself hasn't helped it much. Because of this his blood is poisonous, having properties of his Joker Venom to it. Small amounts of it are not enough to kill someone but it can still induce paralysis and a rictus grin if it enters the body. In canon he is highly resistant to all forms of poisons and chemical attacks (not just his own) but he'll lose that upon arrival. He will remain immune to poisons and chemical weapons of his own design.

pain suppression: The chemical bath means he is also in pain. He's mentioned that he is in pain all the time but he has no memory of life without pain so it doesn't bother him. In fact, no amount of pain bothers him which means he can keep fighting even when badly injured unless the injury is inherently incapacitating, like broken limbs. Not being bothered by pain doesn't mean he takes less damage, of course. He'll die as easily as anyone else. This can be a disadvantage in the long term for him since he does not instinctively know when to flee based on physical pain meaning he tends to sustain a lot of damage. That's especially a problem given that, though he fights with cunning, agility and no sense of fairness, he is not at all a physically powerful combatant. Most enemies can overpower him if he is locked in melee range without his gadgets.

long recovery time: None of the above should give him any sort of advantage in survival but it does all come with a major disadvantage. Medications have unpredictable effects on him meaning it's hard for him to find treatment when sick or injured and it can take longer for him to convalesce because of it.

He is also extremely intelligent (more on that below) and a master at deductive reasoning but this all falls into normal human boundaries.

Joker is a genius engineer (he can rewire TV remotes into tasers) and chemist and he has experience in biochemistry and nuclear engineering so the science of the place will intrigue him, especially once he realizes it really does have him trapped. He is also an expert at turning anything within reaching distance into a weapon. Basically, he has an extremely high intellect and can learn to be competent at many fields of study very quickly. Beyond this, however, he is an alley cat. While he is an expert at life in the city streets, in wilderness survival situations he does very, very poorly. He usually tries to bully his way into a leadership position so he can force people to scavenge for him but even that won't be an option here. Eventually, he will be forced to begrudgingly play nice with others...for a while at least. Until it stops being funny.

He will never be able to achieve the mass panic and chaos that he normally enjoys but he will still try to get under people's skin and drive people apart in this place where cooperation is key. All in all, he will be a villainous presence, but not someone who is likely to be at the top of anyone's list of concerns when just surviving another day is a massive undertaking (which will annoy him because he loves attention). Being an antagonistic character he will also have an extensive permissions and opt-out post.

The setting will make for an interesting exploration of the character. He is very clever and adaptable but isolation is his biggest weakness. This, combined with the lack of a city-wide "audience" or the presence of his beloved nemesis Batman will initially leave him declawed. He will eventually launch into some sort of new performance with time. It would be hard for him not to.

The Joker was used to the occasional lapse in reality. It had become increasingly common practice at the Asylum to try and keep him comatose. Most attempts at landing a cure had been forgotten. Keeping him confined was more important. Unfortunately for the doctors, the clown's biochemistry was so peculiar that he routinely woke up at inopportune times. So it was that waking up with pain in his limbs and no concept of time was not alien to the Joker.

But this time when he awoke it was with an intense, painful pounding in his head. It hammered away between his ears and he curled up tightly into a ball. He was not in a bed; that was immediately obvious. He was lying on some sort of floor, he finally determined. It was unyielding and uncomfortable. And cold. The area around him smelled like ice and frozen metal. However, there were also no voices around him, nobody saying "Go through his pockets!" or "Give him another shot of Thorazine!" and he took this as a good enough start to his day.

Still, he kept his eyes closed and refused to move in case there was anybody close by who, upon seeing him awake, might want to drag him off someplace unpleasant.

When he finally decided to move, he stretched and looked around, seeing nothing familiar. Something had sprung him from the klink and dumped him somewhere else. He was not sure where. The very idea made his sides itch and he decided he'd have to find whoever was responsible and beat them silly. Ideally with a blunt object but he was not in a picky mood.

It was not that he minded being free, simply that he preferred freedom on his own terms. He thrust his hands into his pockets and stumbled through door into the bitter cold, thinking dark thoughts.

Not Gotham. He knew the skyline of his preferred habitat and this was not it. The distinct lack of buildings could attest to that.

If there had been any doubt in his mind as to whether he was still in his home, it was gone now. Something had ripped him away. Away from his gameboard, away from the pieces on it and away from Batman. Now he was God-Knew-Where. All at once he felt enraged, then depressed, then, suddenly, highly amused. It was a pretty funny joke, in a cosmic sort of way. Cruel, yes, but funny. And even if the joke was on him he had to appreciate the humor of the situation.

The clown threw his head back and his body shook beneath the force of his own howling, hysterical laughter.