A gold spirit master wasn't a weakling in reality. It was that William grew much stronger than any of them that made them look this weak.
So when the attack landed, leaving behind a scary rumbling noise, William could only see that ball moving like a lightning bolt, heading fast, away from him.
"Come here!" William didn't know what this ball could do, but he was sure it was able to bring a dark gold spirit master here. So even before his sword would release all the stacked power stored inside it, he activated his lightning technique, chasing after this ball.
"I won't let you get it!"
"I'm closer! I'm getting it first!"
"It's mine!"
"I'm going to stop him!"
And just as William dashed after this ball, all the remaining four moved at the same time. The ball was moving like a rocket, and the distance between it and William kept increasing fast.