As the adventurers approached, a noise was heard from inside the barred off room- something inhuman, and really nothing a rat would make either.

Inside the room laid sleeping four rats, each about the size of an adult human female and with extended stomachs. Around each was a litter of rats, and at the very center of the room was a rather large  treasure chest, a good three times bigger than the ones outside. The chest itself seemed to radiate energy, subtle but strong. At the same time, something within the chest seemed to be pulling the adventurers in, as if it sewed a string into their hearts and began tugging.