The Tainted Sphinx is a Main Boss in Xenoblade Chronicles X. It is a member of the Tainted group as a Sphinx variant infected by a virus. It is fought at level 24 at Millstone Ridge in Noctilum during Chapter 6, after the party retrieves the alien mech. Upon its defeat, three more Tainted Sphinxes appear, but before they can attack the party, a flying creature appears and kills them all. After being defeated in the story, a level 30 Tainted Sphinx can be battled at Oblivia's Barbarich Desert in the Time Attack Mission The Infernal Beast.