Attack of the Faceless People

The princess Serena of the Sun People arrives on Quasar, being pursued by Darkon of the Faceless People. Darkon wants Serena so he can control her people. The Herculoids successfully drive him off but not before he captures Zara. Zandor agrees to a swap but substitutes a berobed Gleep for Serena and they destroy Darkon's palace from the inside.