User: Xeno of Carcosa/Sphinxes
Sphinxes (including their Valyrian kin) are an intriguing part of this world. They are borrowed from our own world, which also has two types: winged Greek sphinxes, with a strong emphasis on riddles and preventing people from passing, and unwinged Egyptian ones, used as statues often flanking entranceways; in both cases having a guard-like role.
In Westeros & Essos, these statues are almost always found at gates and doorways. Towering green marble lion-sphinx statues are outside the gates to the Citadel, there are Valyrian sphinxes outside the council chamber of the Red Keep, and the carvings of sphinxes (whether Valyrian sphinxes or not) on the Long Bridge are on its arched entrance gateway. Even the huge Valyrian dragon sphinx in the Velvet Hills is said to be "crouched beside the road": this is far from clear but "beside" indicates that it and its missing counterpart could well have been on either side of the road, possibly serving almost as gateway and symbol of Valyrian power rather than facing the road as a generous piece of public art. This connection with power is also related to secrecy – the councils of the Red Keep, the knowledge of the Maesters, the mystery of Valyria. Only with the Valyrian sphinxes captured by Euron is the original context completely lacking.
Unlike in Greek myth (where the Sphinx was female), and Egyptian statues, which are usually male, the statues in the books are generally found in male-female pairs (or female-male pairs as the wiki article states from this early edit). Neither sex is indicated to predominate, but their sex is often important in the text. While Tyrion is on the way to Ghoyan Drohe, he sees the female sphinx statue (which he calls a "dragon queen"), while the male statue had been taken by the Dothraki to Vaes Dothrak, in contrast to the Targaryen Daenerys, who had also passed Ghoyan Drohe with Khal Drogo while being taken by him to Vaes Dothrak. The sphinxes outside the Citadel are more ironic – equal male and female statues outside the male-only centre of learning, where the only (almost certainly) female student that we know of is unwittingly called "the Sphinx".
There is also no indication that sphinxes were ever living creatures: no mentions of them are present, and when Tyrion scoffs about tall tales of dragons, his ultimate example is of "dragons riddling with sphinxes... nonsense, all of it". Tyrion also ridicules "dragons with four legs", something that GRRM has said that he specifically finds out of place in fantasy – vertebrates in our world only have four limbs, and so winged creatures (birds, bats, pterosaurs) have only ever had two legs – and sphinxes are an example of a six-limbed vertebrate (body of a lion, wings of a hawk, though it would be interesting to see whether the Valyrian sphinxes have two legs, or four as the drawings produced so far show).
That said, the Valyrians, according to Septon Barth, were said to have "practiced blood magic and other dark arts as well, delving deep into the earth for secrets best left buried and twisting the flesh of beasts and men to fashion monstrous and unnatural chimeras". While it's possible that they were created by the magic of the Valyrians (probably the only way that they could be real in this world), Barth's account is deliberately polemic at this point (for example, it's directly followed by "for these sins the gods in their wroth struck them down"), and as this is the only time that this type of monster-making magic is mentioned (there are many other theories of why the Doom happened, and none even hint at this), it could also easily be that GRRM has made Septon Barth get confused by the Valyrian sphinx statues, mistaking them for monstrosities actually created by the Valyrians, when no such thing ever happened.
It's also worth a quick note though that while the assumption is that normal sphinxes (i.e. any sphinx not specifically mentioned to be Valyrian) are human/lion/hawk/serpent, and Valyrian sphinxes are human/dragon, this is never clarified. It's possible that Valyrian just means that that's where the statues were made, and the precise "bit of this, bit of that" combination of animals could completely vary from sphinx to sphinx.
Finally, while no mention is made of sphinxes in The World of Ice and Fire, the Tales of Dunk and Egg, or Fire and Blood, I can't write this without mentioning Alleras, whose nickname 'Sphinx' works to evoke a bit more "otherness" to this Dornish/Summer Isle character, who, with cryptic smile, black eyes, a love of knowledge, and a dangerous side, seems to have been shaped to match the name. As for Aemon's words: "The sphinx is the riddle, not the riddler." The statement is itself a riddle, but not one that Sam or Alleras seems to know the answer to, even if Aemon ever did. Alleras' almost certain identity as Sarella Sand seems to be the answer, and hints that she may play an important role in Winds of Winter or Dream of Spring, perhaps working in conjunction with Euron following Damphair's vision in the Winds of Winter preview chapter "The Forsaken".
- A Feast for Crows, Chapter 45, Samwell V.
- A Game of Thrones, Chapter 20, Eddard IV.
- A Dance with Dragons, Chapter 27, Tyrion VII.
- A Dance with Dragons, Chapter 5, Tyrion II.
- The Lands of Ice and Fire, Journeys.
- A Dance with Dragons, Chapter 57, Tyrion XI.
- George R.R. Martin, Comment on "Dany and the Dragons", Not a Blog
- Fire & Blood, Jaehaerys and Alysanne.