Siån Phillips: Livia Drusilla, wife of the Roman emperor Caesar Augustus

Sian Phillips was married to Peter O'Toole for twenty years. This bit of trivia only serves to validate my perception of this performer as a powerhouse. Furthermore, that most who perform at above average levels, as both Ms. Phillips and Mr. O'Toole have oft demonstrated, are driven by something akin to, if not precisely, mental illness or personality disorder. More power to them! It is this grade of performer that can really sell this genre stuff. You may or may not recognize Ms. Phillips from genre classics:
Clash Of the Titans (1981)
Dune (1984)
Ewoks: The Battle For Endor (1985)
Notice her piercing, unflinching gaze.