quest question !!!!!!!!???????

[alonehope]

Hi Everyone I was a dark master in somber and just tried to switch side to light after like Idk +1 year
and faced with this quest ...
and I cant just buy banish set like the belt in the shop also bought chest and opened got one banish belt too but still didn't work and why should sts put this rare drop in main side quest ??
if anyone knows some way to throw this quest pls let me know tnx )
IGN: Alonehope