Norma Cenva - God Emperor of Dune

Norma Cenva is first mentioned in God Emperor of Dune by Frank Herbert, when the God Emperor Leto II notes:

Who has ever heard of Norma Cenva? ... You think a man designed the first Guild ship? Your history books told you it was Aurelius Venport? They lied. It was his mistress, Norma. She gave him the design, along with five children. He thought his ego would take no less. In the end, the knowledge that he had not really fulfilled his own image, that was what destroyed him.

This paragraph is the only mention of Norma Cenva in Frank Herbert's works, although Brian Herbert and Kevin J. Anderson develop and expand her character considerably in their novels.