rune trader

can someone tell me why the rune trader ill not buy my rune of minor vigor.
i realize i could sell it in game, but this is bothering me.
ty for your help.

It was undoubtedly from a quest reward in Kamadan. Use it on a hero.

yes....it most likely is a quest reward...but you can also sale to other players as you previously mentioned if you don't want to use it on yourself or a hero

cause minor vigor is reward in one quest in Nightfall. you can sell it to other players or put it on your/hero armor