Before we talk of the Sphinx–gatekeeper sphinx!– it is perhaps wise to review what we know of her nemesis Swollenfoot.
Of his ill-starred birth you know, and of the abandonment that gave him his name. His name, that mocking name! For him was the riddle of the Sphinx formed; she asked, and he wondered (as he must always wonder), did she tease? Did the feet of her riddle take him for their model? Of course. Wrong-footed he started, and so wrong-footed he put her, down among the rocks and the potsherds.
So. Gatekeeper she, sphinx she riddles that none may pass except the right one. Agent of destiny, defender of plague. Not cause of plague; she is herself a riddle to be unraveled, a right clue in the wrong direction.
Half-lion, half-woman, counterpart to the lamassu, the sphinx represents a sharp line between what is knowable and what is not. This is knowledge and that is fancy. This is the true king, the true betrayer, and that is… is nothing. Is empty death. Where the lamassu asserts himself as unity, as godhood, as the One Voice that cries the storms to being, the sphinx is martyr to the unthinkable, to the immiscible: a thousand voices raised in song, none quite alike in pitch, tempo, meaning. Without her there are no categories, no growth, no one who may be king, but she must be surpassed before true healing can begin. Swollenfoot must own his crimes; the sphinx is a gate, but not the destination.