Altered Yuka used her darkness domain when Lan Xuhuo approached. The darkness engulfed the inquisitor and robbed him of his senses. He couldn't see anything. He didn't know where his quarry was. Even if he flew to Amon's last position, he doubted the demon would remain there.
Altered Yuka didn't attack Lan Xuhuo. She remained in hiding after using her darkness domain. Lan Xuhuo wished that she did. At least then he could pinpoint her position and strike back. He was confident he could wound the altered beast badly enough with one move to dispel this domain.
Since the enemy refused to do that, he had to resort to using brute force.
