Based on Xiao Chen's plan, taking down Bone City would still require some effort.

They still had formidable strength, with a continuous stream of monsters entering Bone City from the Undying World, allowing them to amass considerable power.

Even if things went smoothly, it would take a few hours of fighting.

Perhaps seeing Xiao Chen's determination to attack the city, or maybe unable to endure the howling of the Million Wolfkin, the Lord of Bone City decided to abandon the city and flee.