Fighting the Mermaid
As the situation turned pretty intense in another place, Kai thought it would be better to cut the mermaid first before thinking about this. At the very least, he got some clues about why they tried to attack him. And looking at how the turtle seemed to like him to the point he invited him himself, Kai thought there must be something more about this.
He took a deep breath as his team had gone to their respective positions.
"Soldiers, take care of the surrounding creatures and make sure you are not hit by her because I am afraid I can't protect you," Kai commanded and warned them at the same time.
"Yes, Sir!" The soldiers could also understand that and spread around the battlefield. With their eight thousand soldiers, twenty thousand beasts shouldn't be a problem. The only problem would be these two, so Kai needed to kill or at least stop the mermaid from interfering.