When they discovered that the humans inside had already achieved godlike abilities.
The Demon King felt that their undersea world was not as good as the other's Immortal Castle.
The level was different, the quality was different.
Unable to seize it, and not daring to confront them, afraid the others would discover their undersea world.
So they all hid in this undersea world to recuperate.
Thinking they would never interact with humans again.
It's been more than a year, and they have eased their minds, not leaving this undersea world, they could always cultivate to become immortal here.
Enjoy where enjoyment is due, eat where food is needed, cultivation was just a part of it.
Yet, they didn't expect that without going out, the others would come looking for them, and with strong divine beast elves, plus a deity they somewhat feared.
Is this a retaliation?
Is this retaliation for occupying others' land on the surface?
It's been more than a year, why are humans so petty?
