According to the legends, the Nine Streams Flood Dragon had the body of a huge elephant and the neck of a python. It had nine heads and one mouth, which were capable of swallowing all living things. It was known for its ferocious nature, and if one wanted to kill it, they would have to cut off all nine heads at the same time, or else they would have to cut off its head and be reborn, never truly being killed.
It wasn't that there was only one mouth among the nine heads, but that there was a huge mouth of a taotie on his back that was capable of devouring all things. It was something that resembled a White Jade Pixiu.