A Tleilaxu Master named Scytale is mentioned in Heretics of Dune (1984), 5000 years after the events of Dune Messiah. He is one of Tleilaxu leader Waff's nine councillors, and apparently a ghola of the original Scytale:
Every one of them here had been wakened time after time in ghola flesh. There was a fleshly continuity in this Council that no other people had ever achieved. Mirlat himself had seen the Prophet with his own eyes. Scytale had spoken to Muad'dib!
Though Herbert notes little about Tleilaxu Masters prior to Heretics, the novel establishes that after learning how to restore a ghola's memories in Dune Messiah, the Masters use this knowledge as a form of immortality. As in God Emperor of Dune (1981), Face Dancers are Tleilaxu servants rather than emissaries. Herbert does not explain how the Scytale of Messiah — a Face Dancer, though autonomous — could ascend to become a Master, or how the Master-Face Dancer relationship may have evolved over the millennia.
Read more about this topic: Scytale (Dune)