Secretly, however, Bijaz was a Tleilaxu Master with a hidden purpose: to control the first ghola of Duncan Idaho, Hayt. Bijaz implanted the command to kill Muad'dib when the Emperor was in the depths of grief—this was accomplished using the secret whistling language of the Bene Tleilax.
When Idaho confronted Paul after the death of Chani, the trauma restored his pre-ghola memories and he spares Paul. While the plan failed, it is revealed that it was only a contingency; the Tleilaxu were planning to use Idaho as proof of gholas regaining memories, and they were planning to use Chani's ghola as a bargaining chip. However, Paul refuses and Idaho instead kills Bijaz to prevent any more temptation. The Tleilaxu's fate following this incident was unknown. However, it was possible his body was returned to Tleilax and restored to life via Tlelaxu technology, such as occurred with Scytale.