The party is in an underground merchantile enclave. They secretly work for the mages that manage the place but the people in the hall should not discover it. They retrieved a relic that's only valuable for some specific people. It's of drow manifacture and when they bring it to the drow merchant he tells them he recognizes the item and tells them the whole story.
A client asked him, he organized an expedition, the expedition was attacked by the very same duergars that the PCs defeated. So he tells them the item is worthless and offers them 300gp, but the players would like to haggle for som…