When he thought about how he was being forced to leave the South Pole, the Sun King felt a chill that was colder than the power of the icy explosion run through his body.
His blazing yellow eyes made of burning fire twitched, and he said, "So this is their plan. They want me to leave the South Pole. They must want to kill me outside the South Pole, so that they can easily retrieve my core and use it to create a new Sovereign or empower an old one."
He was right to think that the invaders wanted to drive him out of the South Pole. It is true that an explosion of fire was unlikely to threaten his life, considering the kind of power that he still possesses. His resistance to fire damage would have covered the gap between 80C and 100C, and prevented the fire explosion from killing him.
This is one of the major reasons why the three patriarchs decided to use an ice bomb. The second reason is to make the Sun King leave the South Pole, so that they can kill him outside.
