乌桓 / Wuhuan
乌桓 / Wuhuan enters the wiki through Hanji 998 as a northern frontier group participating in the coalition against 公孙瓒. The episode says 阎柔 is selected as Wuhuan sima because of his prestige and then gathers large mixed Hu and Han forces.
Wuhuan cavalry also joins 鲜于辅 and 鲜卑 riders in welcoming 刘和 and linking with 袁绍’s side. In this source, Wuhuan are not background color; they are part of the force mix that makes the anti-Gongsun campaign large enough to break Youzhou’s local alignment.