Nothing original here (and i hope OP will forgive me).
+1 to Menzoberranzan
I really wish to see dark campaign, and drow society. Their culture have potential for dark/mystery/crime/politics stories.
Also, i see a lot of people wants Avernus... what about entire journey through Nine Hells? We could reuse fact about stealing x from Mephisto (i don't remember what was that), or reason could be just simply escape from hell? or something original, new.
Or reuse Wyll, Karlach as a reason.
I don't have great ideas because i don't have knowledge about lore.
