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Sphinxes are giant black feline Grimm with white plating with red marks on their face and spikes along their body. They have sentient snake-like tails, which possess their own set of fangs, which are presumably venomous. Sphinxes also have two massive avian wings covered in black feathers and four large paws with long white claws.
In the episode "Argus Limited", the newly reformed Team RWBY, along with Qrow Branwen, Oscar Pine/Professor Ozpin, Jaune Arc, Nora Valkyrie, and Lie Ren board the Argus Limited train through Anima to Atlas in order to deliver the Relic of Knowledge there and search for the next one. However, during their trip, the train is suddenly attacked by a Sphinx and a swarm of Manticores.
The two Huntsmen named Dee and Dudley go on top of the train to fight off the threat, but Dee is quickly killed by a charging Manticore. Qrow and Team RWBY step in to help, holding off the Manticore swarm while Dudley rushes to activate the train's turret defenses. These hold off the Manticore swarm until the Sphinx Grimm signals for them to take the turrets out, simultaneously bringing them over to the inhabited section of the train. Qrow fends off more Manticores and tells Oscar to tell Dudley to shut off the turrets. However, Dudley sees the turrets killing Manticores and refuses. The train enters a tunnel, giving the fighters a brief intermission before the Grimm swarm the train again.
Team RWBY manages to convince Dudley to turn off the turrets so that they may lure the Grimm to the back of the train. Once there, Ren can use his Sembalnce (amplified by Jaune's) to mask the negative emotions of the passengers. Team RWBY and Qrow would then detach the inhabited part of the train from the back, allowing the passengers to get to safety and allowing them to meet in Atlas later.
The train exists the tunnel and Qrow and Team RWBY begin fighting the Manticores and Sphinx again, this time pushing them to the back of the train. Ren uses his Semblance, hiding the train from the Grimm's view and allowing it to escape. A Mandicore attacks Oscar, but he gives Ozpin control so that Ozpin can fight it off with his cane. Team RWBY then works together to simultaneously beat and dismember the swarm of Manticores, picking them off individually until only the Sphinx remains. All of the fighters team up to take on the beast, with Weiss, Yang, and Qrow trying unsuccessfully to cripple it. Ruby then formulates a plan and has Yang and Blake secure the Grimm down onto the train to restrict its movement and prevent it from flying away. Then Ruby and Qrow simultaniously attack with their spinning scythes, cutting the Sphinx in half. However, before dying, the Sphinx launches one final attack before dying that destroys a part of the train tracks and derails the train, leaving Team RWBY, Qrow, Oscar/Ozpin, and a mysterious old woman named Maria Calavera.
In "Seeing Red", Argus is attacked by a swarm of Sphinxes, Manticores, and a Leviathan.
In "Our Way", the Atlas military fights off the Sphinxes and Manticores while the Beacon students and Caroline Cordovin fight off the Leviathan. After it is defeated, Cordovin tells them that the Atlas military will take care off the remaining Grimm, saving Argus.
Powers and Abilities
Sphinxes use their durable hide and armor plating to remain durable and tough when in combat, allowing them to last longer than other, smaller Grimm. Their teeth and claws are extremely sharp and deadly, especially when they use them in quick slashes. Their wings allow them to sustain flight, and they are shown to be quite agile in the air.Sphinxes also seemingly possesses a shriek that can summon other Grimm (only Manticores have been observed to answer) to their aid or even give them commands, as shown by the Argus Limited train Sphinx "telling" the Manticores to attack the turrets and retreat from the tunnel. They also possess a fire breath, which deals great damage and has a long range.