His attack before at the cage might have awakened the black fox spirit, but it didn't show any sign of being alive so far. It just helped to crack open the cage, and still didn't move an inch from there.
William didn't know for how long that spirit would keep playing dead, and he couldn't risk it as it might take much longer than he expected.
So he made sure to focus on evasion, not fighting and killing. Even if he ended up with lots of wounds, he was sure the moment of the high-end monsters to appear would be delayed as long as possible.
But hours passed, and that fox spirit didn't wake up. "Don't tell me I need to go up there in person to wake it up!" he rolled his eyes while noticing the appearance of many middle-stage dark gold monsters.
They weren't that threatening yet, but if they grew up in number, they'd pose a threat to him. He'd be forced to shift gears and start mass killing, ending up facing the high-stage monsters fast.