The cave

You can hear the rumble from miles away and even then you're too close. Fishermen and merchants whisper stories of a vast hole in the world, where the ocean drops in to darkness, but jutting from the distant center is the unreachable floating island. Many adventurers have taken the plummet, none have returned. The cave is an unknown thing and yet humans try to understand it. And when humans try to understand something so impossible, it becomes evil. But does it live up to the rumors?
Diving into the depths introduces you to a completely different world, of creatures you couldn't even find in the dreams, or nightmares, of a child. The cave holds inhabitants charged with the task of protecting the 6 realms from their sibling. The dark number 7 is what the humans should fear, if they knew it existed. The protectors are pretty good at there job.

Fantasy

The cave is a link between realms. Hidden in the vast oceans of realm 1, it holds the main gateways linking all together, where races could intermingle in peace. Slowly, after the ruler of the 7th realm decided that the other races were too weak, people collected together for a war that would disrupt the peace forever. In a battle that lasted 100 years, half of every race was wiped out before they had time to respond. Peoples of magic combined together in hope of creating a power strong enough to close the 7th rift, the only problem was there were too many creatures all with diverse magic. With the magic refusing to combine the leaders of each race decided to take a dangerous risk, they, along with every other magical creature in the 6 realms, surrendered their magic the womb of an aviatrix destined for twins, and hid her away until the children were born. As the war raged on, the children were trained until there trainers could teach them no more. Their magic flourished and their mighty wings were a sign of hope among the people. Finally, housing the powers 6 of the 7 realms and glowing with immortality, the twins closed the main rift into the 7th realm, ceasing further entry. They then banished the murderous beasts, and peace was found once again. The powers being handed off after many generations to the next set of aviate twins. The land was quiet.
Humans did not understand magic, although a few possessed it and so they gave it to the essence in the children. As new generations were born and the races began regenerating lost magics, the humans, with what little they began with, did not. Out of anger they too called for rebellion against the aviates whom they believed took their power. For many nights they killed anyone they could find and burned everything that could be burned. They were reckless in their search for the woman pregnant with twins, for word had spread. The aviates did not want to fight their human allies, so when the children were born they once again combined their powers in order to freeze the infants in timeless sleep until it was safe for them to be awoken, and then they surrendered. The humans wiped out the aviates entire race in two nights, evicting any creature with magic into the small cave in the middle of the ocean. When the bodies became ash and that ash settled, all that was left was a few books and a couple infants, ignorantly sleeping amongst the ashes of the library. Their caretaker, a young boy yet accomplished warrior, and the only aviate still alive, along with the sleeping children were taken in by a family in a small town full of people who opposed the war the humans had waged. The young aviate had been gifted immortality and the ability to disguise himself as human, for as long as he deemed necessary, in exchange for his service in the ever-present war against the creatures of the 7th realm.
Those twins eventually woke up after 36 years of magically induced sleep and grew up in the village, never allowed outside if not fully and completely disguised as humans, and even then it was rarely. On their 18th birthday, the aviate boy brought the twins, along with the only five books not destroyed in the fires, to the cave in the sea. Many years later, the aviate charged with teaching the twins ended his immortality, believing he no longer had the ability to farther the twins abilities, as they had far surpassed his own.

The magic in this world is all the same. Its like a substance (like an element of the periodic table). The difference in the races magical ability comes from their bodies different ways of using it. Aloisia and Addox can form daggers using the magic by condensing the magic inside themselves into a metal like substance that they can form and dissolve at will. Races with the ability to heal have concentrated magic inside the blood in their hands. When their hands comes into contact with the wound of someone else, the magic will link with the cells of the wounded and will form the missing skin, or patch bones and muscle tissue. In this way the magic does not "heal" but rather replaces until the body heals itself. Races that can manipulate plants transfer the magic into the cells of the pants. They can use the transferred magic to copy the plant cell structure or move them (growing plants and manipulating them).
The magic inside a being is manipulated through neurological links. Magic is an extension of the being almost like an arm or leg however the nervous system interacts with it in a more indirect way.
When the races gave up their magic at the end of the 1st of the major wars they concentrated the magic into what they could and severed the connection internally. This left the neurons weak and is the reason it took a long time for them to regain their use.
The transfer into the fetuses of the twin aviates was done through a secondary source (a healer) who could link the magic to the individual cells and neurons of the still developing children, and by creating new pathways throughout the brain to create links to all the different types of uses for the magic, making stronger links for more powerful/useful powers like the creation of the metal like substance (for weapons) and healing. It took many years overall for the powers of everyone to be infused with the children (people didn't all give up the powers at the same time so that people could continue fighting throughout the process) but by the time the children were almost due very few people ad power left. As the children grew up the healer continued sinking the powers into their cells so that by the time they were 18, and the healer had transferred her own magic, they had all the magic and ability to fight off and seal away the 7th realm. The birth of twin aviates was rare and so each time it happened the previous guardians would use the same healing technique to transfer the magic into the developing fetuses and growing children. The aviate race was chosen due to their already high about of control over the substance that is magic. (originally the link was going to be put into the most powerful of each of the 6 races but when attempted, the 5 races other than aviates experienced brain trauma- loss of control of their own magic, loss of memory...ex)

nadah
well swords i guess

The cave lies far out in the sea, far enough that some people don't believe it exists. No human knows how deep it goes or what's at the bottom.
Those that inhabit the cave, the humans call elves. These elves are the descendants of the few humans whos magic had returned to them after the end of the War of 100 Years. During the Wiping of The Flyers (the term the humans use for the war in which they killed all of the aviates), the humans took pity on their human counterparts whos magic had returned, only if contained in the cave and island floating above. Along with the elves, the humans pushed all other magic possessing creatures in due to the spite they have for never gaining their own powers back.
Inside the cave lives a vast system of intermingling cultures. Peoples from the other 5 alliance realms trade and live cohesively under the noses of the humans. The many cave systems are home to a surprisingly diverse number of ecosystems.
The Inner City
The Floating Island