When he heard Marvin say that the key was actually the Book of Nalu, Yin was filled with regrets.
This name might not ring a bell to some ordinary people, but old foxes like Yin were very familiar with the legend of the Book of Nalu.
Yin simply didn't believe that Marvin would be able to collect all the pages of the Book of Nalu!
And even if he really managed to do so, that still might not be a good thing.
The story of the death of that powerful God was a lesson that the Book of Nalu was incredibly dangerous.
But he was in a good mood after collecting the Vampires' Secret Precepts, so he decided that he didn't mind Marvin keeping the cloak. Instead, he gently reminded, "Don't you think something is wrong?"
'Wrong?'
Marvin was puzzled.
He was about to ask for clarification, but before he could, the book in Yin's hands suddenly burst and shrouded the Vampire Primogenitor.
