While often times a Sphinx will use indirect methods to herd a party (or person) they will also use intimidation to obtain these goals. They will even go so far as to impede their targets travel directly by asking an impossible riddle. If the party gets the riddle correct, they will allow passage but if they get it wrong they will kill any that attempt to pass.
Once a location has been visited the Sphinx will move on to other lands.
While the Sphinx are physical powerful beast their true power lies in their developed Psyche Skills with a special focus on the Life Sense skill and the Mentis Magi skill branch to aid in communication as the do not have a spoken language.
read more here.
All the Best,