The Yotur as a people had their start several hundred years before the two worlds collided with one another, when a tribe of nomadic humans searching for the next place to live for a time came upon the island. They saw the island was large, had room enough for all of them but also had rich fish stocks and a healthy supply of birds for eggs and meat. Not only that, but the tribe found several edible species of plants on the island that they could reasonably grow. After a brief meeting among the elders, the Yotur people agreed to settle on the island, which they named Halic, for that meant "paradise" in their tongue.
They lived comfortably on Halic for several hundred years, staying with their traditional methods of living for hundreds of years. They never saw a need to change what had worked perfectly for them in the past. They prayed to the spirits of the ocean and the land both, cherishing them with gifts of both food and drink, different kinds depending on the different kinds of spirits. Then the two worlds collided, and the Yotur found their faith realized like they'd never thought of before.
When the worlds collided, the Yotur were quickly visited upon a great spirit of healing which saw the tribe as a way to help hmans, and so it did. For a thousand years the Yotur and this spirit (simply called The Healer) lived together. The Healer didn't lord over the tribe, but he did accept sacrifices from the villagers, but only their own blood or the blood from animals, as it empowered him. The Yotur and him lived peaceful lives together, until around 1000 years passed.
Then, a strange plague hit the island. It was incredibly virulent, and was so potent that not even The Healer could remove it completely. The pleague became so bad so that The Healer advised the tribe to vacate the island, saying that it had been "tainted" and that it was no longer safe for them. The elders brought up the point that the disease would be able to spread if they left the island, but The Healer was able to alter the diease somehow, meaning that if someone was over water, they could only be infected if they came in contact with another person, and that even if they went onto land the Yotur would have a week before they got infected from the air.
Unfortunately this used up almost all of The Healer's power, and so as the Yotur began to evacuate the island he settled into the ocean, going into a deep sleep to regain his power. The Yotur used their week well, building either floating or stilted cities over the water in record time, moving as many people as they could off the island. There were a few Yotur on the island after a week had passed, and they were left there so as not to endanger the community.
And so the Yotur remain, living on their floating and stilted cities, waiting for The Healer to return and cleanse the island. To help this along, the Yotur have begun sacrificing animals over where they say The Healer was buried, in the hopes that this will speed up his recovery. Every now and then some of the Yotur hear strange noises from the ocean, so they continue to do this. They have also renamed the island. It is now Halic-tor, which in their language means "false paradise".
Halic-tor is a large island that the Yotur rarely trample on for fear of the disease, knowing as the Spirit Plague for how it seems to infect not only humans, but any spirits they're bonded with as well. The Spirit Plague affects regular humans, people with sparks, and people with pacts in different ways. With normal humans, it simply causes intense seizures and vivid hallucinations depicting nightmarish landscapes and horrifying creatures. After a period of time an extremely vivid hallucination is triggered that causes the body to go into shock, dying shortly thereafter.
Humans with sparks react somewhat different. They receive the seizures but the visions are instead given to the spirit that has provided their sparks. The more humans sparked to the same spirit the more vivid and intense the hallucinations are for the spirit. Eventually the spirit will be driven entirely insane by the visions, and the seizures will put so much stress on the ghuman's body that it simply stops working.
Pacters receive a somewhat different responde. To them, the disease is entirely transferred to the spirit, whether there's a familiar or not. The spirit will grow erratic and slightly insane, and may even attempt to take control of the power within the pacter. If there's a familiar it will begin to look sickly and diseased, with pieces rotting off of it and bloody pustules forming on the familiar. Afterwards the spirit will die, and the pacter's power is changed. Whatever abilities they had before, their powers are now focused entirely on disease and sickness and they cannot be changed.