This is a theory about the origin of certain islands in The Legend of Zelda, The Wind Waker, if you want something that will chill you to your bones, head elsewhere.
Spoilers for Ocarina of Time and Wind Waker.
For those who don't know, the Legend of Zelda series follows a specific timeline. The part of the timeline that is crucial to this theory is that Wind Waker comes after Ocarina of time. According to the timeline, after Link defeated Ganon, Ganon returned years later and was able to take over. The goddesses of the Zelda universe, in an attempt to stop Ganon, flooded the land of hyrule and created the world that Wind Waker takes place in. Here are my ideas as to the origins of some of the islands in Wind Waker.
Ice Ring Island
Ice Ring Island is all that remains of Zora's domain after the flood. This island is very similar to the Ice Cavern in Ocarina of Time due to the obvious ice correlation and the fact that the Iron Boots are received in both Ice Ring Island and the Ice Cavern. Wait, didn't Link obtain the Iron Boots in Ocarina of Time? Why would they still be there? At the end of Ocarina of Time, Link was put back into his younger self by Zelda after defeating Ganon to warn Zelda of the impending takeover. All of the items that adult Link received would be gone due to the fact that the events in the future never happened, so the Iron Boots would remain untouched.
Dragon Roost Island & Fire Mountain
Dragon Roost Island and Fire Mountain are what remains of Death Mountain from Ocarina of Time. Dragon Roost and Fire Mountain both revolve around fire, are relatively close to each other, and are in close proximity to a great fairy. In Ocarina of Time Death Mountain was a single mountain that revolved around fire, and had a great fairy on it. There were two parts to Death Mountain in Ocarina of time, Dodongo's Cavern and the Fire Temple. My theory is that Dragon Roost is Dodongo's Cavern and Fire Mountain is the Fire Temple. In Ocarina of Time there was a ring of smoke around Death Mountain, and in Wind Waker there was a ring of smoke around Dragon roost. In Ocarina of Time, the entrance to the Fire Temple was too hot for link to enter without a red tunic. In Wind Waker you need the ice arrows to be able to get into Fire Mountain. I also think that the dragon Valoo from Wind Waker is actually Volvagia from Ocarina of Time (or one of his descendents) since Link killed Volvagia in the future timeline, and the future timeline never happened.
The Forest Haven is Kokiri Forest. This is explained in game, but I'd like to talk about the formation of the island itself. I believe that the first island (the one with the Great Deku Tree) is actually the petrified remains of the first Great Deku Tree who died during Ocarina of Time (the child timeline, so it really happened). As for the Forbidden Forest, I'm not sure if it's the lost woods or something different altogether. It could be the forest temple, but I can't find anything that seems to link them together.
I believe that Outset Island is what is left of Lake Hylia. The labyrinth underneath the stone head is the water temple, or at least that's what I think due to the vertical layout of both of them. Another thing that links the two is Jabun, who I believe to be Lord Jabu Jabu. Jabu Jabu, in Ocarina of Time, had barely any backstory whatsoever. This is just speculative, but maybe Jabu Jabu was found by the Zoras in Lake Hylia. It certainly would make sense given that Zora's Domain and Lake Hylia are linked, and the place where Jabu Jabu resides in Zora's domain is so small it's hard to imagine him being born there. Perhaps once the flood occurred Jabu Jabu could leave Zora's Domain and take up residence on Greatfish Island (which could also be Lake Hylia). Once Greatfish Island was destroyed though, he went back to his old home of Lake Hylia on Outset Island to hide. Of course it is possible that Outset island could be the remains of Zora's domain, but that would leave the aforementioned Ice Ring Island in a sort of grey area because the islands are so far apart.
And that's all I got, I hope you enjoyed.