Jimmak Cenva was a misborn on the planet or Rossak. Supreme Sorceress Ticia Cenva was his mother, but she only looked at her son with disdain. When Jimmak was born on Rossak, his genetic 'weakness' was apparent and he was placed in the jungle to die. However, Jimmak and several other Misborn survived and lived on. Jimmak would assist the Rossak men in their hunt for pharmaceutical plants for VenKee Enterprises.
During the resurgence of the Omnius Scourge on Rossak, Jimmak took Raquella Berto-Anirul into the jungle after she contracted the plague. The water used from the cenote pool stopped the Scourge and enabled Raquella to recover. Raquella awoke already at the pool and had no idea how to get back. Jimmak would not reveal the pool's whereabouts because of a fear that it would be taken away from the misborn. Raquell's survival contributed to her ability to change her own body chemistry to 'disarm' any poison. The final episode of her evolution came when Ticia Cenva attempted to poison her and prevent any antidote to the Scourge.
Nothing else is mentioned of Jimmak after Raquella's survival and Ticia's death.
Jimmak only appears in Dune: The Battle of Corrin.