The Rupturing

Originally the Archipelago was a single island called Pelata. This large island was ruled by the Colossus of 4 elements, fire, earth, water, and air. These were peaceful beings however were always trying to one up each other with their creations. While many magical beings were made they culminated in the created of the genasi.
This final creation however brought far too much magic into Pelata, causing a rupture of immense power which resulted in a large magical explosion. To prevent their creations being wiped out the Collosi sacrificed themselves to protect them. This in turn created The Archipelago, which still retained a very magically charged atmosphere.
This is what brought about The Rupturing  and turned the island of Pelata into what is now known as the High Seas Archipelago today.