Sphinx of legend

[Quick Leaf]

What would you expect out of an encounter with a sphinx of legend?
Besides the riddles of course. Are there any sources for such a creature?

I'm thinking of trickery...For example, dressing a group of recently killed criminals as the PCs, mangling them, and displaying them around her lair, maybe dropping one off in city. While the PCs are gone, reports spread of their death, such that on their return they are treated as ghosts.
Another thought is hiring mercenaries to attack a caravan through intermediary, then chasing them off, gaining respect/better reputation.

Some powers for a Sphinx of legend are definitely a deafening roar, perhaps a fascinating allure, and an oath to not kill anyone who beats her in a riddling match.

 

[Mark]

Which type of Sphinx? And how powerful is the party currently?

 

[Quick Leaf]

The party is high-level 14-18. The sphinx was sent by gods to punish hubris of man. It did its job and decided to stay, having developed a taste for man flesh. It's technically female, but I think it deserves a better stat block than the gynosphinx offers.
They can't just kill the sphinx for two reasons. One, they are believed by populace to very possibly be avatars of a demi-god who was sworn not to kill any beast sent by the gods. Two, there's a group of knightly protectors who would lay down their lives to protect the sphinx, believing it to be a divine creature!