Corruption. Many societies have fallen by its hand, many more have risen. It is eternal, as long as the human being exists, corruption will be there, because it lives in the man's heart.
Fear. Fear feeds on the man's soul, slowly devouring it, corrupting it. Making it become a carcass. Fear emanates from the unknown, and there shall always be things unknown: thus, fear.
Anger. Anger is what motivates lots - that destroys most. Anger is what makes the man self-destruct itself, when struck with pure anger and hatred. Anger lives from the person's bad situation: which everyone eventually passes.
And last but not least, regret. Regret exists as much as past actions do, because it steams from them. No one's perfect, nor are their doings: people always regret past decisions.
Azkaban was a place where all this reunited itself, and broke the prisoners' minds. No one can resist the anguish, the freezing atmosphere of the prison. The dementors only enhanced the mood, breaking the sinner's mind faster.
Not even the most powerful Occlumens could resist its mind-breaking atmosphere. Not even Sirius Black's regular cheerfulness and strength of will could save him from breaking down after some years in Azkaban, not to mention that he had an "exclusive treatment" – courtesy to his parents' hatred for their old son. These old timers were killing him from the grave, and deep down he knew he deserved it. To rot in this prison, fed just enough to live, but not enough to think. He was a vegetal, but a thinking one at it. That was the bad part: he was the dementors' favourite prey: not yet dead, but so close to it that he was their easiest food; full of good memories, didn't have the will to retain them.
However this would all change. His lawyer – since he had one, though it was clear that the man was as biased as Crouch had been – had arranged his transfer to a muggle asylum, pleading insanity to the Muggle Prime Minister: a particularly low blow for the Ministry for Magic, since it meant that they weren't capable to resolve their own affairs. The Other Minister, having heard of Black from the current minister, had accepted the plead after being assured that the mass murderer was in a vegetal state. He was to be transported to some American asylum – the only nation that had accepted a guy with such background.
Maybe this was a new chance. But this time he knew Dumbledore wasn't right. This time, if he was caught and arrested under the banner of Lord Voldemort, the charges would be right.
He would see Harry again, no matter what.