The Blue Lightning Tortoise Technique
Arthur wasn't a defensive type of a man, not right now, not back when he was a cultivator. He leant over offense and saw the strongest defense was by using the deadliest attacks.
Yet when he was on the verge of walking directly inside the den of his enemies, he had to consider ways to sustain not only his life but also the lives of his army.
Not to mention he would be vulnerable if he lost big at the start, he needed his hard trained armies to be ready for the upcoming fights over the nine remaining worlds.
So when he was lost at first to choose a defensive technique, the first thing that popped up in his mind was an area defensive technique.
When he gave it more thoughts he was astonished to realize he never looked for defensive nature mages. It seemed that his own nature affected the way he attracted mages to him in this world.