Two formidable experts from the Ming family, taking advantage of the fact that everyone in the Dantai family was focused on the duel with Chen Tianyang, first set fire to the Library Pavilion to lure the defenders away. They then seized the opportunity to infiltrate the Langya Secret Treasury and stole the Dantai family's peerless supreme martial arts manual—the Seven Divine Transformations of Shenzhou Sutra—thus rendering a monumental service to the Ming family.
That is how the present scene came to be.
"It seems this is the Langya Secret Treasury. It certainly has an air of majesty."
Chapter 999