The power of fire gradually weakened, and the power of water began to emerge, but in the end they still could not escape the fate of being split into two, and eventually split into the Ice Tribe and the Water Tribe. After the Water Tribe was defeated by the Ice Tribe, they fell into the Palace of the Seven Seas, reproduced for generations, and became mermaids. However, they never forget revenge, and the string bridge leading to the third world is broken. In addition, what is the curse that can control destiny?