The book says that at the junction of Nanyue, Beiyuan, and Western Chu, there is an extremely mysterious forest constantly shrouded in white fog that kills people.
Any creature that approaches it, whether human or beast, gets killed, except for a strange creature called the White Rhino.
The White Rhino is all white and has four horns on its head, allowing it to move in and out of the white fog without harm.
Qi Yue, following the map, found this place and discovered it was actually at the westernmost end of Longnan Ridge.
She concluded that the mysterious white fog was miasma, and about the creature's four horns, she thought they differed from those of the current White Rhino.
However, after thinking it over, she felt that the four horns might have been a mistake in transmission.
After all, it's common for recorders not to see such mysterious creatures clearly, or perhaps they exaggerated for the sake of myth.