Statue by Norman Lindsay
Sphinges are not omniscient, per se, but they know everything. They were the first beings created by the gods, and the sky god Summanus created their eyes from the essence of his indestructible body. Thus, they may see anything that occurs anywhere in the world, and they will never die of natural causes. They may be killed, but they will never decay - worms, moisture, and fungi will do nothing to them. Fire cannot burn them. If you wish to be rid of the corpse of a sphinx, then you must hack its corpse into little bitty pieces, every cut filled with intentionality.
They have had since the dawn of time to learn, and so they have learned with certainty all physical laws that govern the world. A sphinx knows all the rules. They have, essentially, all the facts - if an event occurred more than 3 hours ago, a sphinx has already learned of it. They cannot read minds, however, and they cannot tell the future with certainty, for it has not occurred yet. They know enough about all men to know what is most in character for them to do, but they can still be surprised. If you have lived a virtuous and simple life, and in your secret heart of hearts have held a desire to catch a sphinx in a big net and flay it alive, then the sphinx would not know this - unless you have ever spoken it aloud, or acted sufficiently shady in preparing your big net.
Cast a handful of sand into the wind, and a sphinx will be able to predict, with absolute certainty, where every grain lands, even with its eyes closed. They have what economists wish all mankind did - perfect access to perfect information.
Perfect knowledge has made the sphinges grow bored and idle. Most of them have abdicated the earthly world and dwell now in the Plane of Clouds, partaking of the hospitality of the elemental lord Hirroo. They occupy themselves with contests of riddles between one another. A riddle, to a sphinx, is no mere tricky question, article of trivia or game of wordplay. Everyone knows the one about Man, and the one about A Coin, and the ones about A Coffin, Saint Elmo's Fire and Comte Escavoir de Sigons VIII. Occasionally, if a mortal is insistent, they made condescend to ask such questions, but the sphinx gains nothing from this - it's like when you ask a 4-year-old what color the sky is, and then congratulate them when they manage 'bwue!' on the third try.
Riddles between sphinges are deep, elaborate labyrinths of many layers. Most people call them 'conspiracies'. Men and their kingdoms are a sphinx's playing pieces - sphinges do not crave power, and act with mere gentle nudges from a great distance, but they create great webs and mystery cults to draw in their ageless fellows. Their designs are so subtle and so far-reaching that they unfold across continents and over the course of decades or centuries - but they have all the time in the world to play. Typically, "Where is the sphinx's riddle" and "What question, exactly, is it asking me with this whole mess of secret societies" are deeply tricky questions that must be untangled and answered before one even starts on "What is the answer to the riddle".
