Historicity
Since the Battle of Banquan is treated historically by Sima Qian in his Historical Records, it would appear that this is a pivotal transition point between mythology and history. Ironically, Yandi enters history only with his 'demise', which it seems was submission to the will of Huangdi, rather than actual physical demise. In any case, the title of Yan di apparently lapsed at this time, while his tribe's descendants were said to be perpetuated through intermarriage with the party of Huangdi (see Descendants of Yan & Huang Emperors).
Read more about this topic: Yan Emperor