FF8 Ultimania includes an epilogue about Hyne explained by Kazushige Nojima. Farplaner has translated part of it for this site. Hyne's story is then continued in the actual game's text as the legend of Vascaroon, which was transcribed by Asyria. It shouldn't have to be mentioned but for posterity's sake, this Hyne has no relation to FF3's Hyne.
In the beginning, there was Hyne. Hyne controlled the world because he had great magic and was able to win the battle against all the monsters invading from the moon.
From where Hyne sat, in the east, he couldn't see the ocean as there was a mountain blocking his view. So he created humans to help him "move the mountain".
He became tired and fell asleep as the humans did the job. When the job was finished, the humans wanted to ask him what to do next. Since he was asleep, they did whatever they wanted.
Hyne finally woke up and was surprised. There were so many humans now, so he burned the small ones with magic. The humans complained about the small ones, children, being burned but Hyne only saw them as tools. So he took away their ability to communicate with him.
Once upon a time there was a person named Hyne. Hyne was the ruler of the world. He became lazy and decided to make a tool to make his life easier. Hyne made a neat tool. His tool could make more tools by itself. Soon there were a lot of tools in the world. These tools were actually people.
When Hyne woke up, he was surprised because there were a lot of people. Hyne wanted to reduce the number of people, and used magic to burn up a lot of small people. The small people were children. The people cherished the children very much. So the people rebelled against Hyne. Hyne used powerful magic to fight them. The people couldn't use magic, but they had wisdom.
Eventually, Hyne began to lose the war, because there were too many people to fight, and they were getting smarter. Therefore, he decided to make peace with people by offering them half of his body along with his powers. Hyne cut his body in half and gave the people half as he promised.
Then, another war started. People began to fight over the power Hyne offered them through his body. This war lasted decades. Finally, King Zebalga and the Zebalga tribe emerged victorious and demanded Hyne's body-half to get its powers. But the body ignored their commands.
Then, Vascaroon came to the rescue. He appeared before the confused Zebalgas and revealed to them that Hyne's half-body was corrupt and possessed no real power. The body-half was actually Hyne's castoff skin. The Zebalgas were angered by this truth, and decided to destroy Hyne. The Zebalgas never found Hyne. People began to call him "Hyne the Magician" and continued to hunt him for centuries to come.