Yun family belonged to 1of the 12 protector families for the demon emperor of demon contenent (illusory demon realm) on BPS.
But why serve demon emperor and why even ice phoenix, golden crow and other god’s spirit didn’t even recognise YC’s(yun family)bloodline/race. Well, mars has hinted about it when the HSDE said to YC that BPS came from NGR. And now he
has given his answer for that in the latest chapter that yun family also exist in NGR like any other reigon, because its a common family name, but YC’s clan’s bloodline came from NGR and this clan wasn’t created by a creation god but a demon emperor.
And there’s also revealed in this chapter that yun clan was punished because they betrayed the demons and stole the profound treasure ( most likely MoS).
So i speculate that, out of the 7 profound treasures 4 of them; ancestral sword belonged to Mo E, SoLaD to Li Suo, space needle\spear to Evil god, Eternal heaven pearl to the “extra guy” ( don’t know his name at all, and the last 3; SPP belonged to HSDE, Eternal wheel of myriad tribulations to Moon Slaughter devil emperor, and last but not the least MoS to “the one who hadn’t been introduced yet demon emperor” .
When at the end of the gods and demons war the eternal night devil clan activated EWoMT with SPP, at that time or some time before than that yun clan’s royal family or something had taken away the MoS along with them and hid on the BPS and that’s why BPS had MoS and yun family. Because i don’t think yun clan was created by EG or HSDE or else she should have mentioned it.
So, yun clan might have been created by the Demon emperor which had MoS with him that could answer why YC could use MOS and it was on BPS because EG gave them shelter on BPS. Now, as for how the current plot is going YC will learn about his clan’s origin, save them, gain control of them, control NGR, use them for revenge or something like that. He may also gain a better understanding on MoS and how to use it. That’d be all. ( ̄へ ̄)