King Neptune was seriously injured by that slap from Shuangtian, but he could only spit another mouthful of blood and retract his words. Right now, his kingdom's capital was in ruins, hundred of soldiers and civilians were dead, his nobles and allies had been knocked away into some corner and his daughter was held by the enemy.
Even worse was the fact that his people's heirloom, the Golden Trident, something forged for Poseidon and passed down to Neptune, was seized like this and his connection to it was fading.
Neptune had never been soberer in his life. His millennia of sitting on the throne and managing this kingdom had dulled his mind, because the most the dealt with on a daily basis were mundane issues.
They never experienced crises, they never experienced calamities. When the Demons came every thousand years, you for sure know that they avoided the water world, so the Kingdom of the Undersea did not even have a clue about the Great War.