The appearance of the Sin-you is similar to that of a Qilin, but more feral and imposing. It is a large quadruped with a feline or ovine body, a shaggy mane, and is either depicted with hooves or feline paws (the latter often to stress its difference from the Qilin). In has a single, unbranching horn in the center of its head, like a western unicorn. The Sin-you’s eyes are said to be very intense and imposing, figuratively burning into whomever it gazes at in a predatory fashion.
The Sin-you is highly symbolic of justice, and is believed to have the power to know if a person is lying or know if they are guilty with a glance. It sometimes depicted at court beside the ruler or judge: if a person told a falsehood in its presence, it would leap forward and impale the perjurer though the heart with its horn. In other instances, the judge would put convicted murderers before the Sin-you, who would slay them in the same fashion if they were truly the perpetrator, but leave the innocent unharmed.
There has been some cryptozoological theories about the origins of this creature. It has been suggested that a mutation may have occurred among a rare species of predatory feline (such as the North China Leopard) which caused the growth of a bony protrusion from the skull. Among such a small gene pool, it is possible that such a mutation was propagated for a period of time, making it appear as a new species of horned felines.
- Rose, Carol M. (2001). Giants, Monsters, and Dragons: An Encyclopedia of Folklore, Legend, and Myth. New York: W.W. Norton & Company. p. 377. ISBN 0-393-32211-4.
- South, Malcolm (1987). Mythical and fabulous creatures: a source book and research guide. Westport, Conn: Greenwood Press. p. 16. ISBN 0-313-24338-7.
- Leeming, David Adams (1997). Storytelling Encyclopedia: Historical, Cultural, and Multiethnic Approaches to Oral Traditions Around the World. Phoenix, Ariz: Oryx Press. p. 474. ISBN 1-57356-025-1.
- Gould, Charles (2009). Mythical Monsters. BiblioLife. pp. 357–359. ISBN 0-559-10836-2.
- Conway, D. J. (2001). Magickal Mystical Creatures: Invite Their Powers Into Your Life. Saint Paul: Llewellyn Publications. p. 25. ISBN 1-56718-149-X.