He studied that nine tailed fox for a long time, trying to get to the bottom of its power. And he thought he knew enough, but it seemed he didn't know a thing.
It had the Devour ability that William never knew anything about. And now he learnt about the presence of another scary ability, the Nine Lives ability. In addition to that, that fox wasn't just focused and adept at the darkness element as he thought. It knew more elements, including time and space ones.
Adding everything together, William suddenly saw the face of that old bastard smirking back at him. He didn't need a foresight technique or ability to know that he'd fail if he continued down this path.
"He said that this bastard scattered many of his spirit seeds into lots of worlds. That means… I have to take down these copies first before fighting that damn bastard…"