桓典 / Huan Dian (late Han)
Hanji 922 introduces Huan Dian, courtesy name Gongya, as a descendant of Huan Rong who teaches the Shangshu at Yingchuan before serving as shi yushi. The source emphasizes his stern censorial reputation: eunuchs fear him enough to avoid his route.
The episode attaches him to the later phrase “骢马御史” because he rides a piebald horse while on duty. In the wiki, Huan Dian is a personal counterpoint to late-Han 君臣反馈失灵: one official’s reputation can deter court favorites locally, but it does not reverse the broader eunuch-protection structure visible in the same episode.