Magic was a funny thing. It could twist the laws of nature, of physics, to suit its whims. Though the Wizards and Witches of Earth had come to use their magic for amusement and to make their lives easier and more comfortable, when structure was applied to magic it could create wonders that the Wizarding World had never even dreamed of. In the same breath, when magic was allowed to run wild and free with no interference ... Well, the word extraordinary did not even begin to cover it.
The connection of Azkaban Prison and the Library of the Clayr was one such instance, where the logical rules of nature had taken leave of their senses. Logic had no place here; magic had twisted that which should have been, and created something else.
One the one hand, there was Azkaban. Once a home, then a fortress, and finally a prison; an island now filled with so much sorrow and sadness that the darkness seemed never to lift from it's shores. Beyond the shores of Azkaban an entire world stretched out, both magical and mundane.
Yet at the lowest reaches of Azkaban lay a passage leading into a sunlit world. One had to but step beyond the last doorway in order to find themselves within the Library of the Clayr, the whole of The Old Kingdom stretching out beyond it's borders. Encased within an ancient mountain, the Library held the only entry point into the realms of Earth, though the passage of time had eradicated all memory of this passage from the minds of those who had safeguarded it.
Connected through a single passage, hidden beneath the Rock and stone of the Clayr Sanctuary, Azkaban had remained forgotten and silent, it's only occupants the sendings created all those centuries ago. The Free Magic which permeated Earth to it's very core had twisted these once docile creatures, until all that remained were the Dementors - creatures twisted by the pain and fear which surrounded them.
When Azkaban first became a prison for the damned and the forgotten, these creatures had not been a part of it. No Witch or Wizard had known of their presence, for they remained in the lowest levels of the fortress, away from the prying eyes of the Free Magic users above - a magic as different from their own as to be nearly indistinguishable.
But the Free Magic of the Wizards and Witches of Earth had seeped into this place, corrupting and changing these creatures into what would, one day, become the Dementors of Azkaban; creatures as different from those original Sendings as night was from day - as Chaos was from Order.
Where the Free magic of Earth met the Charter Magic of those long-ago visitors from another world, the strange and the impossible walked hand in hand and became the commonplace. Time moved differently here, in the lower halls of Azkaban Prison; so slow, in fact, that one watching from a distance might imagine that it did not pass at all.
One might live out their entire life within these halls, buried deep beneath Azkaban Prison, while a mere handful of hours passed above. Days, weeks, months, even years passing by in the time it took to cross from one room to another - an entire life wasted, seeking a way to cross a barrier of magic that had become warped and disjoined, without that chaos destroying the traveler.
Harry Potter knew this very well - he had already spent more than half a decade in the pursuit of such a goal.