It was indeed the West Rat King.
"Lu Qingshan, mission accomplished." The West Rat King was extremely excited, looking as if it had made a great achievement, with a storage ring clasped in its mouth.
"I emptied their treasure vault!" the little rat demon boasted.
"Well done." Lu Qingshan nodded, took the storage ring, and upon probing it with his divine sense, discovered it was filled with various minerals, materials, books, demon soldiers, and so on...
Thieves never leave empty-handed.
The West Rat King, highly talented in this field, had emptied everything it could find in an extremely short period.
I would call you the Treasure Hunting Mouse.... Lu Qingshan mused to himself.
He glanced again at the now ruined Feather Demon City, activated his mind, and retrieved three flying swords.
"Time to go."
He never underestimated the Demon Race.