King Leoric traded sword strikes with Aina and gauged her power, speed, and reaction time.
As a former Saint, he had fought many battles, and had a front row seat when the Abyssal Creatures descended upon the world.
In short, he had very rich battle experience, which he still retained even after death.
After exchanging a few blows with Aina, the Wraith King finally understood how to effectively neutralize her without killing her.
According to Keoza, if Aina was killed inside the Domain, she would be expelled from it and returned to the real world.
This was not the scenario that they wanted, and their goal was only to neutralize her. They needed to buy time until Keoza patched up his Domain, preventing Aina from escaping it.
Fortunately, Aina seemed to have no intention of leaving until all of the enemies in front of her were dead.