sphinxlike

adjective2

1. •
   Like a sphinx, or like that of a sphinx, especially, not showing passion or emotion; inscrutable.

   • they get together in the dry riverbed. He writhes over her for a minute or two as she sits sphinxlike, dignified, head straight in the air. — 2020
2. •
   Mysterious; scheming; having a deceptive outward appearance.

   • Mrs. Mallowe smiled in a superior and Sphinx-like fashion. — 1889