I am not completely sure, but from my understanding Sothis came to Fodlán peacefully, created the Nabataeans who lived alongside the natives, helped the natives out by sharing skills and technology with them which lead the natives to prosper and become the Agarthans, who at some point started to considered themselves gods and started to conquer and kill Nabataeans and destroying the continent so badly that Sothis had to spend so much energy to repair it that she went to sleep for a couple years, and this is when the red canyon tragedy happens.

Basically, the natives tried to betray the people who helped them become a modern society for no reason at all.