Am I alone in wondering why Gringott’s Bank has recently taken to guarding its High Security vaults with sphinxes? I was taken aback to find one of these creatures standing guard outside my own vault on my last visit. As I failed to answer every one of the sphinx’s riddles, I was unable to get past it to my gold; indeed, I consider myself lucky to have escaped with my life..."
-- Mallory Twiddle, Letter to Gringott's Bank (DP1)
A Sphinx has the head of a human and the body of a lion, the capacity for human speech, and an innate love of puzzles and riddles, but due to its violent tendencies it has been placed in the ‘beast’ rather than the ‘being’ category (FB).
- The sphinx has been used by wizarding folk for centuries to guard treasure, and is noted for violence when that which it guards is threatened (FB).
- In the opinion of one of the Bestiary's editors, the sphinx is very probably a wizard-bred species rather than a naturally occurring one, given the remarks made by Scamander in his footnote on acromantulas (FB), but we have no definite information on that point.
- A female sphinx was stationed in the Triwizard maze both to guard the closest approach to the center and to provide a hint about the last monster guarding the Triwizard Cup. She required an answer to a riddle; once the riddle was solved, she calmly let Harry pass by (GF31). Harry later listed the Sphinx as one of the "foul things" he had to cope with in Fourth Year (OP4).
- Cornelius Fudge had to let the Muggle Minister know about the three dragons and one sphinx imported for the Triwizard Tournement (HBP1).
- Gringotts has been known to place sphinxes to guard some of the vaults, much to the consternation of those who want access to their valuables and aren't particularly good at riddles (DP1).
Stories of sphinxes originated in ancient Egypt.
A commonly held idea in mythical stories is that sphinxes are exceptionally wise, and the reason for their riddles is to see if those they ask are even able to think through things enough to understand what they will find out if the sphinx lets them.
While the date printed on DP1 is 31 July 1998, the timeframe for these events is 1992-1993.