Ysionris Jeromi

Admiral Ysionris Jeromi was the Chief medical officer of the UNSC Research station Hopeful. He was a personal friend to Dr. Catherine Halsey, and performed a number of expirements on Binobo chimpanzees for Dr. Halsey. She was his star pupil, and he had never approved of her working with the Office of Naval Intelligence. He was a mentor to her and his dissaproval made her decisions more difficult. The experiments he conducted were later used on the Spartan soldiers.