Mentats

In the aftermath of the Butlerian Jihad, computers and other forms of thinking technology were banned due to the OCB's commandment against thinking machines ("Thou shalt not make a machine in the likeness of a human mind") and, at the same time, the anti-AI laws had been placed in effect; the punishment of owning such AI device or any kind being immediate death. Human computers, also known as Mentats, trained as replacements to the mechanical thinking technology, just as the all-female Bene Gesserit and the Guild of Navigators took up the same functions that had been previously covered by the Thinking Machines prior to the Jihad which banned all thinking technology.
Mentats are used extensively by the Great Houses, primarily as political advisors. Thanks to their vast memories and ability to organize huge amounts of data they often provided valuable insights that would otherwise be lost. Limited Mentat training was also used to augment individuals destined for other political or military roles.
Syn Hekatas is the Mentat Master of Assassins for House Cul'thir. Valyar Gorin acts as House Cul'thir's treasurer and is a mentat trained in accounting. Ullya Hino is the head of Spice operations for House Cul'thir on Arrakis. He is a mentat trained in management.